66 here. Damn straight I wonder about it. Cannot do things that I could do just a few years ago due to back problems -- can't exercise as much, can't carry as much weight, and overall less stamina. I am at the point where I wonder how much longer I should continue, although clearly I can dive just fine -- but I never carry the gear (which I used to do just a few years ago).
I called DAN about it some months back, and their comments struck me like what you might get from an insurer - they were saying that you must consider not only what you need to do in the water, but what about an emergency situation? Can you handle a strong current, maybe hanging onto a rope? Can you get back on the boat if necessary? Can you walk out of the water onto shore if need be? That sort of thing.
That sounds like where I am - I could do those things, but since it might take my back out I don't.
- Bill