great post general masterclass.
we might as well throw in another variable:
these all time great guys have been ultra competitive in life from the day they were born.
they just hate to lose.
Federer has massive skills that are not going to fade away if he keeps playing. I would start making the transition to doubles if he wants to compete until he is 43 or so.
he can do it. it would be a great way to stay in the sport he loves and also keep winning.
I would play fewer tournaments but play both singles and doubles.