I had better say something here about this question of age, since it is particularly important for mathematicians.... No mathematician should ever allow himself to forget that mathematics, more than any other art or science, is a youngman's game... Newton gave up mathematics at fifty, and had lost his enthusiasm long before...Galois died at twenty-one, Abel at twenty-seven, Ramanujan at thirty-three, Riemann at forty... I do not know an instance of a major mathematical advance initiated by a man past fifty. If a man of mature age loses interest in and abandons mathematics, the loss is not likely to be very serious either for mathematics or for himself."
A Mathematician's Apology, 1941
Note: Do you agree with this statement....can you find counterexamples?