Some old guys get stronger at the grind with age. My grandfather played marathon sessions even into his 70s that my friends and I couldn't keep up with. We'd have to convince him it was time to leave a casino or sometimes sleep it off and he'd still be playing. It was even worse in private games he hosted. There's a point of course where everyone declines but in things that take mental stamina some people keeping increasing it seems late into age, I've witnessed this in a few different professions.