From a Scientific American blog:
Albert Einstein once commented that “a person who has not made his great contribution to science before the age of 30 will never do so.” This may have been an accurate reflection of physics in his time, but it is no longer the case—for physics or any other field. Benjamin Jones, an expert in innovation at the Kellogg School of Management at Northwestern University, and Bruce Weinberg of Ohio State University analyzed 525 Nobel Prizes awarded in physics, chemistry and medicine between 1900 and 2008. With a few exceptions—notably quantum mechanics discoveries of the 1920s and 1930s—the trend across all fields is toward researchers being older when they produce their greatest work.
That is an idea to be tested in economics. One would also expect that the main contributions in economics are done when laureates are not that young, but not that old either. Probably in the 30s. But again that is an empirical question.