Earlier quoted context omitted.
I think the question is different for the typical chess player compared to those at the very top. And at the very top we don't have that much data... going back to Fischer, he had a short career and disappeared by 32, but not really for lack of ability. For Karpov, his reign lasted about 10 years from age 24-34, but even after that he was in the top 3 or top 5 for another 15 years until he retired in his 50s. Kasparo…
> his same-generation rival Karpov Karpov is 12 years older than Kasparov.
Good point, it was sloppy of me to call them same-generation, I distracted myself with thinking about Kasparov's long reign at the very top which I view as defining a sort of competitive era ("generation") that was shared for the majority of Karpov's active career at the top levels as well, even though it extends past that and Karpov had his own period prior to the Kasparov rivalry. It's interesting to bring that back to the question of how much age matters though since Karpov kept playing and was also still very strong against the even newer players (Anand and Kramnik being 18 and 24 years younger) for most of the 90s too.