I’ve seen just as many 40 something year olds who can’t seem to turn away catering, whose sole exercise is carrying their overnight kit over the hotel curb and are a heart attack/stroke waiting to happen as I have seen older pilots who need to hang it up. Man, I’ve seen more than a few younger pilots who probably won’t even fit through the escape hatch on the 747. Personally, I think that should be a demonstrated requirement- fitting through your aircraft’s escape hatch.
Everyone is different. Just because one person can’t wait to hit 65 doesn’t mean that should apply to all.
But yeah, as you age you need to look in the mirror and be honest with yourself. Maybe tighter medical requirements.