There is an interesting article and discussion over at TheServerSide.com about Impact of Overtime on Productivity, which of course resulted in the comment that programming is a work of the mind and mindworkers cannot really be focused and productive for more than about 6 hours a day. The rest of the working hours are spent chatting at the coffee machine and checking mail.
I’ve started to believe that 6 hours is what you get out of a good day and usually you get a lot less. So what you really need to focus on is trying to get something productive out of those hours and not spend them all in meetings.