And Euler (e^pi+1=0 discovered when he was 43). And Hilbert (published the axioms of geometry when he was 37 and formulated the Hilbert Problems) And Newton (34 when published Principia). Grigori Perelman (40). Andrew Wiles (41 when proving fermat's last theorem). Michael Garey was in his 30's and Richard Karp was in his 40's when they published their papers on NP Completeness. Paul Erdős published continuosly throught his life (died at 86). Emmy Noether developed Noether's theorem when she was about thirty, and developed Ideal Theory when she was in her 40's.

Hardy's statement was not researched, or scientific. It'd be interesting to actually take papers, take the age of the authors, weight by citation rate, and give a better number of when mathematicians 'peak'.