The most devastating fact of life is that physical (and mental) performance drops off at around mid 30s. Hakuho, by far the greatest sumo wrestler in history, retired at 38 when he should have retired years earlier.
Different faculties peak at different times. While MIT/Harvard research shows that raw processing speed peaks early, it highlights that social intelligence and crystallized knowledge don't peak until our 40s or 50s [I]. Specifically, the Whitehall II study identifies age 45 as the inflection point for initial reasoning decline [II], while research from Stony Brook found that changes in brain network stability—the metabolic cost of cognitive maintenance—typically don't begin until age 44 [III].
[I] https://journals.sagepub.com/doi/abs/10.1177/095679761456733...