I retired in 2001 and continued to tutor math at these sites.
I'm sure this has kept my brain cells activated and will contunue to do so.
I still remember all the theorems and formulas that I've taught.
(But I don't remember what I had for lunch.)
If you're wondering if you're too old for this, . . here is a check-list.
If your knees buckle and your belt won't . . .
If your back goes out more often than you do . . .
If you bend down to tie your shoelaces . . and you wonder if there's anything else . . you can do while you're down there . . .
If your wife says, "Honey, let's go upstairs and make love," . . and you answer, "Darling, I can't do both" . . .
If you can't remember names, . . then you can't remember faces, . . then you forget to pull your zipper up, . . then you forget to pull your zipper down . . .