NYT ran a series of interviews with persons who are “at the top of their games” even into their 80’s and 90’s. This exchange with Christopher Plummer is illustrative
I keep hearing that staying in shape is crucial past a certain age. Anything else?
Yes. And so is doing the work. It uplifts you. The idea that you’re doing what you love. It’s very important. It’s very sad that most people in the world are not happy with their lot or with their jobs and they can’t wait to retire. And when they retire, it’s like death. . . . They sit at home and watch the television. And that is death. I think you’ve got to continue. We never retire. We shouldn’t retire. Not in our profession. There’s no such thing. We want to drop dead onstage. That would be a nice theatrical way to go.
The introduction is by Lewis Lapham. It ends this way
I.F. Stone, the most relentless investigative reporter of his generation, had uncovered the truth known to both Hokusai and T. H. White, and the lesson I’m now almost old enough to learn: that the tree of knowledge and the fountain of youth are one and the same.