[yesenadam]

This may be off topic, but I don't believe "most chess masters" are under 30, whatever MZ meant by that exactly. ("Chess master" is not a term used in chess.) Most top players seem to reach their highest rating between 35 and 45. Looking at ages of the current world top 100[0], about half seem to be over 30, half under. There are not so many players over 40 or 50 at the top these days though. A classical chess game often goes for 5,6,7 hours, and playing a tournament means doing that every day for a week or two. As most players reach 40 or 50, they start to fade after 5 or 6 hours play. It's stressful and tiring - a single mistake often can lose the game, and lose many hours work, sometimes lose weeks/months/years work.

[0] https://www.2700chess.com/?per-page=100