I "work" from 8:30 a.m. to 5:30 p.m, but in fact I'm very unproductive, especially in the morning, and I get only a few blocks of 2-3 hrs where I am productive (maybe 5 out of the 10 hours total in a good day).

I was a lot more productive with other time arrangements (and space, I'm in an open office with 7 other developers, which kills my chances of being "in the zone" unless I wear headphones).