Having managed to get older, now 60, and hopefully wiser, especially regarding such lunacy as trying to party until 3 hours before transport (as I'm sure many of you of all ages have done in the past) I find that advancing years have endowed me with the ability to sleep much more readily and soundly than in the past. I have also manged to control my alcohol intake and my diet such that I am probably fitter and more sober than at any time in the past 40 years.
I do more daily exercise than ever before and in my spare time I play a better game of golf than previously. As for my mental condition, well, I would judge that it is pretty much as good as, if not even better than, it was 30 years ago when it was befuddled on several occasions with too much booze, the effects of which turn even the most enthusiatic and apparently competent youth into a gummer.
I stopped flying at 59 because a) I could afford to, b) I emigrated and c) I began a new, philanthropic career. Had I chosen to do so, I'm certain that I could have continued flying several more years, maybe even to 65 and beyond.
I would only suggest that if anyone wants to continue the same stamina sapping regime as for the past 40 odd years, without savouring the fruits of a well earned retirement, you need your head examined!