[probablybroken]

I find I tend to write bugs after around 7 hour's work, and during the first four, I can throw myself at a new task in a way that at the end of the day I'd be utterly incapable. I think shorter office days would benefit most mature developers. ( I say mature here because I've worked with people who only manage to get things done through many hours extended foot dragging and procrastination. If you can focus, short days can be beneficial. )