When do creators do their best work?

Randall Jarrell similarly observed that "[Wallace] Stevens did what no other American poet has ever done, what few poets have ever done: wrote some of his best and newest and strangest poems during the last year or two of a very long life."

In contrast:

[Jean-Luc] Godard has directed scores of movies in a career that continues today in its fifth decade, but there is a strong critical consensus that his most important single work is his first full-length movie, Breathless, which he made in 1960 at the age of 30.

Those two passages are from David W. Galenson’s forthcoming Old Masters and Young Geniuses: The Two Life Cycles of Artistic Creativity.  Here is a related working paper.  Here are many other interesting papers.

My question: Which economists have done extremely important work after the age of 50?  Have done their best work after 50?  After 40?  Comments are open, I welcome your suggestions but it is not easy…