Hmm, it's an interesting point. I'm not sure how well it holds up for the historical examples, though. Plenty of people (like Mozart) did lots of things early, but plenty also did lots of things later. Is one the predominant mode? I'm not sure, really. Some examples of people who did their most world-class work in their 40s or later: Descartes' famous works were ages 41-48; Newton's Principia was at age 44; Darwin's magnum opus was at 50; Pasteur discovered pasteurization in his 40s, and did his important work on vaccination in his 50s; Fleming discovered penicillin when he was 47. Of course, there are many examples besides Mozart who did most of their work in their 20s or 30s as well, so a bunch of examples don't really settle it in either direction.
