Sometimes I just read something online that says something so perfectly, so well-researched, that rings so true, that I couldn't hope to add anything to it. So, I submit to you the following.
(credit to Cryponomicon for sending me the link)
An interesting discussion of the relation of the length of the workday and the work week as it applies to productiveness and quality. The ten-second summary: for more or less 100 years now, all the greats of organizational design have known that the 8 hour x 5 day work week produces the best level of productivity out of people for a large selection of activities.
Of course, he ties this in with the "ea_spouse" scandal, and how in many technology companies, the lessons of the past have been forgotten.
Read it, you'll enjoy it. Though I hope it does not ring too true for you.
I have to wonder... those 5 hours a night I often do... perhaps when I feel frustrated at my lack of productivity or ability to work through a problem, perhaps I'm just drunk on fatigue? It sure would explain a lot...