No one has proven to me that critical discoveries in science and engineering (or any other field) came from people working themselves to the point of exhaustion as a matter of course.
Sure, the overworked and overtired can write more lines of code for e-commerce Web 2.0 apps and crank out lots of papers that relate to someone else's discoveries. But they won't be figuring out how gravity works anytime soon.
(My point being that too much faith in and reliance on this approach will cripple our ability to make breakthrough discoveries, and I think we've reached that point.)
Very little about why people succeed or fail is ever "proven".
It is my impression from reading the book "Founders at Work: Stories of Startups' Early Days" and other biographies of accomplished people is that there WERE critical times in their lives where they were obsessed with work. Hours per day worked may be difficult to define. When Einstein was at the peak of his career, he was probably thinking about physics, at least subconsciously, for much more than 8 hours a day.
