I'm happy to agree that you perceived higher productivity. But there's an open question whether it was more than perception. Tired people, for example, think they can drive much better than they can. A comedy staple is the non-fine person shouting, "I'm fine!"

I believe that for certain sorts of work, 80-hour weeks might be more productive than 40-hour weeks. E.g., digging ditches (at least for the very young and very healthy). But in software the costs of error are so high, and so hard to trace back, that it will take very solid studies to convince me that the increased error rates from long hours really are counterbalanced by the large number of hours put in.