[spinor]

What about Hardy's collaborator Littlewood, who continued to do excellent research into a very ripe old age?

Hardy was a depressive, and this may have had an effect.

How many of the great mathematicians used Cocaine or amphetamines--not a silly idea, look at how many students use such drugs--to get early success. Recall that Cocaine was LEGAL in the 19th century. Does this explain their early burnout, and the bipolar depression symptoms ( called repeated nervous breakdowns) of so many of the great mathematicians in the 19th and early 20th century?