I have been very fortunate to remain in excellent health, as I approach the middle of my sixth decade.

As I've gained experience in this hobby, my tastes have sharpened considerably. I'm still open to exploring, but I know more clearly what to avoid.

The first factor is our sex drive which varies from person to person and from time to time.  

which is to say, that I find my attraction and performance is predicated upon chemistry between the provider and myself.

or 3 providers new to me in a year. I have several ladies who I continue to repeat with because the experience is just off the charts. You never know when someone is going to retire or move away so I think it is important to always have a plan B available.

It depends on what you mean by exceptional. Like you said, each guy's exceptional is different. There are two types of ladies who can still do it for me. They are exceptional in that they can get me charged up. At this point that criteria is taking a greater precedence than any criteria of old. I don't think that's picky. It's simply adjusting to ever changing needs, and preferences in what's a turn on.  

if you haven't become more selective in all your decisions as you age, then what the hell good does experience do for you?  Experience is what tells you " I'm never again eating sushi from a gas station"   or " I know now not to put a screwdriver in the electric outlet to see if it's hot"  

Thank you for sharing gentlemen!

Its been an evolution for sure.  At the beginning was looking for the low hanging fruit, variety.  Once I felt secure secure in my access to a variety of women, which took about 5 years, I got more comfortable repeating.  

I've for sure become more selective in who I choose to see, which is the evolution of homing in on what it really is that I'm seeking in a date.  Being a TER member has sure helped that process along (the value of reviews).  I've hit some bulls eyes (the chemistry thing), which has been my catalyst for no longer being random with choices (little head rarely gets the final say anymore).  Sometimes the chemistry is sustaining and has led to many many repeat visits, sometimes not so many as the chemistry wanes over time.      

It's a very interesting question and I think it is particularly applicable to older guys.  The reason I say this is that as we get older and aren't as quick on the trigger as we used to be, secondary stimuli become increasingly important, at least for me.  And the principal secondary stimulus, as far as I'm concerned, is physical attractiveness.  When you're younger it's easier to soldier your way through when the mate isn't lovely.  When you're older it's more difficult.

I've been rather picky/selective, since I first started hobbying so I really haven't changed much over the years.  Although, I tend to search for providers who prefer the company of us older guys, since I've reached "senior citizen" status. LOL   I'm also rather sporadic when it comes to how often I see providers, since when I'm traveling, I tend to hobby more than when I'm at home.

...as knowing better what I like and what I don't want, or be willing to "put up with" kinda stuff.

... sometimes the chemistry is just better.  I have to think back a long way to remember a poor encounter. As I get older I find I'm more attracted to ladies with some life experience.

I started this about 9  and a half years ago.  Feels like there are less girls that I would consider.  Pickier or just laser focused??  I don't know.  I visit Houston often and have for years.  There is only one girl that I would see there.  When I do go now, I look to see if there's a hot visiting lady, or go out to a civvie club or strip club.
Just don't know anymore!!

... than I did when I started what I'm looking for in a provider.  It took me about six months of experimentation, and improving my screening skills, to find the perfect fit. And that provider is still my ATF.  I've met other exceptional providers over the years, but some of them have retired.  So I have a very small number of favs whom I see regularly, and only see someone new if someone pops up who looks like a good fit.  I guess you could say I've been spoiled.  

My story is just all fucked up.  Years ago I could finish with any female. But now days at my advanced age 77.  It seems like the only ones I can finish with are the overweight, ugly one's..   Every time I go see a beautiful young hard bodied girl I strike  out.  It's not that they do anything wrong, it's all on me and I think it's a mental thing. So far they all have been very nice to me and understand my ED problem. Of course I never tell them that I can still cum with the other kind of ladies.  
One of these great ladies I have been seeing since I started this hobby at 69, she's hot, beautiful, hard body, and in great shape, I've seen her once a month but all of a sudden after about 5 years I just couldn't finish with her, haven't been able to since but I still see her regularly and still have a great time.  I guess as long as she get's paid she will just go on treating me like a stud.  She still makes me feel like one, finishing or not.