Or maybe doing 35 hours of work in 70 hours.

I'm not sure how many hours I do, probably around 35. I start at around 8am and work till about 6, but take long breaks during the day.

I find that I'm much more productive if I take a lot of breaks -- long hours don't necessarily result in getting more stuff done. I've never had a problem getting all the stuff done that I need to do, and I tend to be more productive than most other developers I've met. In fact, sometimes doing no work for a day or two is a good way to limber up for a difficult project.