We inhabit our bodies, they are our "homes" in a certain regard. It makes really good sense to take good care of your body . . . cause you have to live with it until you die!!! No trade-ins, no trading up.
I knew a guy who ran marathons at the age of 60. I'm not into that, but I think if you take care of yourself you can continue to be physically active until late in life. I suspect that as you get older you will have less endurance (being able to push all day long, sleep, wake up the next day and push all day long, for a week on end). I also suspect you will recover from injuries more slowly and perhaps incompletely. Even so, I don't read this to mean you can't backpack back into the mountains on an elk hunt at the age of 65 years, not if you have kept your weight down, your cardiovascular function high, and your muscle mass in place by working out. But this is just my opinion and it isn't based on personal experience. I just turned 49 last Friday, so this topic has interest for me. I'm not ready to hang it up yet and start hunting on an Internet hunt site from my easy chair!!!
But maybe the point is to appreciate our gift of good health. Tomorrow some fool may slam into us in a car and shatter our leg and those backpack elk trips into the wilderness may be over for us, due to a permanent hitch that develops in that leg full of stablizing pins.