Hey Vagabond,
Speaking only for myself (who will turn 55 my next go round), I have been physically active non-stop in one form or another my entire life, as well as given attention to dietary issues (hats off to my dad) since I was in high school (back in the 60's, oh so long ago!)
One huge additional factor is that I did not trash myself in the days of my youth (I've never had a broken bone). Those who quote the "scripture", "That which does not kill me, makes me stronger", do NOT know what they are talking about. Some injuries, even seemingly minor ones, do not always heal 100%, thereby leaving you with a compromised situation wherever they occur. (Please refer to my many anecdotes posted elsewhere in the OVER 40 forum regarding this issue.)
As far as my specific history goes, I've shot baskets (not necessarily played in games) most of my life. My PK was simply a tangent off of that activity. After a good session on the courts, from 45-90 minutes, I would just work my way back to my truck vaulting and tictacing off of whatever presented itself. I also run through parking lots pulling a few simple moves on my way to whatever errand I'm running. Living near the beach in beautiful San Diego, I also pull "dawn patrol" sessions bodysurfing just about every morning year around. By trade, I'm a self-employed cabinetmaker, which provides plenty of "weightlifting" opportunities throwing around tools and materials. Add all those factors together, practice MODERATION in all things, and you can look to be healthy and active well into old age. I am the same height & weight (5'11'', 150 lbs.) as when I graduated high school...and I have no plans to slow down any time soon.
Noticed on your profile that you live in Reno, NV. Happened to pass through there this summer on my way to my sister's wedding in Nor Cal. We stayed at CircusCircus (yuck!), but had a great little PK session early one morning that I mentioned in another post in this forum--check it out.