I get around 3-4 sustained development productivity (of course, there are always other non-development related tasks to do). If necessary, I can push this to 7

I get around 3-4 sustained development productivity (of course, there are always other non-development related tasks to do). If necessary, I can push this to 7-8 hours a day sustained for about 4 days, but then I need days to recharge afterwards before I really get anything done again.