I'm a director of my own company and everything we do is on a price, so the quicker we finish the quicker we can get to the next job, we try and book as many jobs as possible hoping to get finished on the first one to allow us to make the start date at the next. Gets a bit hairy when we have delays as the building isn't ready.
Many a time we've done 16 hour days, but I try to keep it to 50-60 a week at the minute, I find it gets a bit counter productive if you get over 12 hours a day. Plus I end up with loads of paperwork to do in the office once I'm home so I'm up against it there!! Will be easier when we finally adopt and the good lady is at home and can get the paperwork sorted!!!