When is a fighter’s prime now and why do you think it has changed over the years?

Years ago, in the 40s and around that time, fighters would often be washed up by late 20s, mainly due to not knowing the effects of hard sparring combined with how many fights they’d have, also without focus on recovery and steroids, these days with all that in mind, we see fighters in their prime more so at around 30 carrying through to around 34, this could be due to steroids preserving their athleticism when they wouldn’t if they weren’t on it, whilst they still improve technically, but then again, we’d see the odd fighter in the 1940s-50s still be good in their mid-late 30s, so I think punishment taken is far more of a factor than not taking p.e.d’s.
What do you think?