I've been better and better at viewing time off work as an investment into increasing the quality of the most important parts of the work that I do.
Most things don't matter as much as we make them seem, so better be more selective and make sure that the things that have the most impact are done well. So I really refuse to believe that there are many jobs which require more than 10 hours x 5 days of effort. If so, the problem is likely not that the workload is too big, but rather that one is failing to prioritize and/or delegate tasks.
My problem with work is different. My work is my hobby. Then the border is non existent, and you may end up working 70-80hours per week without noticing. And your body then fails you... That sounds pretty much me at the moment ^^