DP Colin and I met out retired "Family Doctor" when we were doing our weekly shopping. He still walks 5k each day. He is about 90. He still has no problem with remembering medical issues from 25 years ago, our interests, hobbies etc.
When he retired from practice - (for the second time) at about 70 or so, it took up playing golf and learned to play the piano.
I like the three doctors who now have his Practice, but his style of "Doctoring" is sadly missed.