we all age differently and that is the rub. if your genes are of the type to keep you active in old age then stay active.
there was a photo in a National Geographic I saw in the doctors once. it was just a woman at a service station putting petrol in the tank of her Toyota.
the caption read " this photo would be totally unremarkable except for the fact that the woman in the photo is 114 years old."
if you can then do.
I also worked on a ward once where the nurse in charge pulled me aside.
she asked me to give the old guy in the end bed a little extra care. he was losing his marbles.
"ten years ago he was the brilliant doctor who ran this ward".
I'm still aiming to be active at 100.