As I age (just turned 70) my refractory time is getting much longer that I'd like.  What do you think the recovery time should be for a 70 year old, in good shape.

Learn to count your blessings. You're still alive & capable. Life is good. 😊

I would say at 70, if you able to get an erection enough for sex, you are ahead of the game or at least on par. Many men on these boards in their 50s, and some even their 40s, say they can only go once.  
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I am curious what your refractory time is, generally, since you mentioned it. If you are able to go twice in a RW date (or p4p one) in just a few hours or less, I would think you would be in the top 10-20% at your age, but this is just a guess as I am no expert.

There are so many variables. For me the girl makes all the difference. Some have it some don’t.

to two or more hours, you are probably not going to want to continue the hourly donation while you wait for Mr. Johnson to wake up from his nap.  You should only book enough time for one shot.  They go back daily if you want to.  

But:   There were a couple of times recently where a gal decided that I was going to get a second pop, within an hour of the first.

 
So, they really turned on the juice and got me hard again, and son-of-a-gun, they did just that.

 
It was hard work for both of us.   But it was worth it!

 
There are things you can do to improve your odds:   First, take really good care of your body.   Eat right, exercise, keep your weight and blood pressure in normal bounds.   Drink lots of water.   Good hydration is key.  Get plenty of rest.   Meditate to reduce stress.

 
Also, while Viagra does help with erection, it impedes ejaculation, or at least in my case it does.   This can cut both ways, but if you are seeking a second pop, maybe go without or break the pill in half.

Im older and i jack off a few times most days of the week.  

When you get older you have to use it or you will lose it.  

With an anal nymph that will attack my taint and balla after i blow to get me going again, i can keep going and going as long as the reciprocal energy is there. Most of you guys should be able to as well.

i am happy as long as there is ANY refractory period .. days weeks   doesn't matter!  LOL  just as long as there is a next time!!