It varies by person but recovery for a second pop can take longer. I can get two at times and other times only one.
In my younger days (I can't believe I'm saying that) I could go 2, 3, 4 times in an hour. Obviously the latter is pushing it, but when the vibe was there I could do it. I would often read reviews of providers and the client would say "I'm a one and done guy now, so...." etc. I am 35 years old, but recently I've been just that, after I initially cum I don't feel the urge or need to "go again." I feel my hobbying may be coming to an end. This question is mostly for the men who participate in this hobby or just life in general, but I welcome providers insight as to how age differences and performance levels vary.
diet and overall fitness play a big part...the body's ability to have blood properly flow throughout is important obviously.
Testosterone treatment is very popular these days also, you have seen the commercials for the underarm stuff, but I know it can also be delivered to the body in other ways. It's worth talking to your doctor about. Might be something you can do.
If cumming several times in an hour is important, then looks like you are in decline and that really sucks!
But if other things about participating in the hobby are important, then you can have fun for a very long time, to a very advanced age if you're lucky to live a long life.
I'm pretty much a one-shot guy now except on real long dates, and I have a blast. It's been said before but worth repeating: for some of us, it's not about the destination but the journey.
It varies by person but recovery for a second pop can take longer. I can get two at times and other times only one.
I'm 37 now and for the most part I'm good with just once. Every once in a while I'll just keep going so I know it's still in there. I think the biggest factor is that as I have gotten older I have come to appreciate quality over quantity. I really enjoy just taking my time and thoroughly enjoying the ladies I'm with for the entire time (which can sometimes last most of the session). I have noticed with recently getting in better shape my stamina has greatly increased. Now if you can't last more than a few minutes and then can't get going again that might be an issue. If that's the case then try to pace yourself a little. It's always more satisfying to complete the marathon instead of just the 100 yard dash.
...having just recovered from an extended period if health related impotence...
But, at age 50, I get one shot...and I make it count...
Granted I recovered faster in my twenties, but I couldn't last anywhere near as long as when I was in my 40s.
I routinely had sex four, five even six times a day throughout my forties, which of course I could also do when younger, but I had so many fewer opportunities. Now I have opportunities, but it's a rare day when I have sex more than three times in a day.
At 35, maybe instead of booking one appointment expecting to get multiple pops, try scheduling a couple of different appointments a few hours apart. If your wallet can stand it of course.
I will confess, at my "advanced age" most of the time the moment I cum I lose all desire to fuck again right away, unless I am with an exceptional lady. I do enjoy a blow job after a few minutes of rest though.
Wow! You are a sex machine. 4~6 times a day with multiple dates, can't afford the time!
I routinely had sex four, five even six times a day throughout my forties, which of course I could also do when younger, but I had so many fewer opportunities. Now I have opportunities, but it's a rare day when I have sex more than three times in a day.
At 35, maybe instead of booking one appointment expecting to get multiple pops, try scheduling a couple of different appointments a few hours apart. If your wallet can stand it of course.
I will confess, at my "advanced age" most of the time the moment I cum I lose all desire to fuck again right away, unless I am with an exceptional lady. I do enjoy a blow job after a few minutes of rest though.
but nothing like only a few short years ago. I no longer have any desire to see four women in a single day, although I will confess, there are days when on vacation that I will see three. The mind is willing, but the body just isn't interested in having that much sex anymore. I know the day will come when I won't even want it everyday, but I hope that day is decades in the future.
At your age, you are still a machine. I hope I can even do half of what you can do. Don't worry about lose interest. If you lose the desire, you lose nothing, unless you have nothing else to do in your life.
I do love sex with the right partner, HOWEVER, I am not and never been into marathon sex. 20 minutes for us both and I am done, satisfied and ready to do something else.
I guess I get board and once I come, well I am done for at least 5 or 6 hours. This is real life I am talking about.
Best timing for me is in the morning and then again in the evening.
The peak remained in place till my mid-40s, then I noticed a precipitous decline, especially by my mid-50s.
But I did take steps to stem the decline: Better diet and exercise are key, but also I've learned to like the social aspects of my gal pals. I do fewer dates with fewer gals, but they are longer and more satisfying in a way.
To each their own, but I'm enjoying the hobby more than ever now.
(Being divorced and living alone has also helped the last twelve years also.
I almost never try to fuck after my second bottle of tequila, that never used to be a deal breaker until recently. After one bottle I can still fuck, but rarely cum. Alas, the concessions we make to get our dicks wet in our old age. lol
Because like AC/DC says, you're already there
Most of us have been where you are. But, as with many aspects of life, one learns to compensate for the impacts of age.
I can't match the exploits of GaGambler, but as a youngster I would pop in 20 minutes and be ready to go again 20 minutes later. Age began to greatly reduce that ability.
However, with age I also learned how to please a woman. I learned to relax, take my time, extend the fun. That coincided with the ability to get an erection and keep it a long time before climaxing. I keep myself in great shape, I eat right, sometimes I get alittle help from my pharmacist. Now, with the right lady, I can easily go 4 hours of consistent action. I will repeat, I've learned how to please most women.
Ain't it great how nature works
Don't sweat it....as most have already said....savoring, being creative, attentive, and taking your time will be even more enjoyable.
I've found that, unfortunately, as I've gotten older, I got a lot more winded and tired afterward. Last year, there was a period where I exercised a lot and got in real good shape for me. Got rid of the spare tire and felt great. And I noticed the sex drive came right back again. I could go all night. Now that I've gotten out of shape again, I'm right back to being "one and done." 
No two bodies change the same way. There is no "normal." Get a thorough physical to make sure nothing else is going on. If that's clear get your self some viagra!
And stop worrying!
I once saw a lady who spoke of an 80 something client who could pop 5 times during the hour session. So I'm pretty sure it's different for every guy. As for me, the decline started in my forties, then dropped off a little each year. That being said, there's also a roller coaster aspect to the decline. There are moments of brilliance, but those become less and less with each passing year. Now that you've noticed your own decline, you get to start the game of finding the right magic potion.
I have done more than one in an hour but the 2nd for me just was not that enjoyable.
More like work!
Certainly, do not leave hobby for that.
I try to take a bit more time in other areas like hand holding and cuddling.
We were raised in a society where sex is copulatory only, ideally between a female and a male and it ends with male orgasm. What the fuck? we are conditioned so bad to this belief that we measure our sex skills purely on erection and ejaculation. Well, that is just not true and now you have to work on breaking the mold you have been living unaware trapped in. This actually represents an opportunity to reframe what is intimacy, companionship, foreplay, afterplay (hell, I had amazing sex in second rounds I never to got to end). The purpose of sex is not to come; the purpose if to get aroused, connect and share that closeness to lift your mind, body and soul. I highly suggest you read The Erotic Mind by Jack Morin, a must read; and maybe take a look at Chris Donaghue's Sex Outisde the Lines which points at different points how ignorant and oblivious of it we are.
Do not take my answer as criticism, rather as some advice; for me reading these books and becoming interested in the topic and looking at shaking up the constraining accepted idea of how sex should be has been tremendously enlightening. You may find that you enjoy sex in years to come much more than you did in the past.
I'm 28 and have always been a once and done guy. Even in my sexual peak of around 20yrs old. In rare cases I can do twice but never more than that. I usually need until the next morning to recover, and really don't feel the need to be relieved again until a few days later. My ideal frequency of sex would be about once every 3 days, minimum is once per 7 days, after that it starts getting uncomfortable.
And to top it off I have no longevity, never have. A sexy lady who knows what she's doing (so any woman I would have in my bed) can make me explode in 3 mins.
I will tell you what, being this way doesn't go over well in the civvie dating world. But the ladies in this hobby LOVE me for it. Which makes sense. The lady only has to spend 10 mins of our hour "working". Then we just cuddle and chat for the rest of the time. And that's fine by me, cuddling is my second favorite thing to do after fucking.