I've worked 12+ hours 6-7 days a week at multiple points in my career for an extended period (the longest lasting 8 months). In my most recent case (which was 1

I've worked 12+ hours 6-7 days a week at multiple points in my career for an extended period (the longest lasting 8 months). In my most recent case (which was 10 years ago), I was starting a company with a friend and we signed client contracts very early. We knew what we were obligated to build. I learned Javascript, CSS, and PHP (coming from a background of embedded C/C++, Python scripting, and Linux/Unix administration) at the same time as I shipped a vertical-specific CMS. I didn't have a family, significant other, or other time commitments and so I could focus 100% of my energy on the joys of learning and building. I don't know that building a large CMS tuned to a specific vertical is trivial, but it wasn't the most technically challenging problem I have ever worked on. There were a boatload of details (especially in the analytics and traffic arbitrage modules), very tight deadlines, and entirely new technologies to learn. I was getting normal amounts of sleep per night (5-7 depending on how I felt) and when I was tired, I'd take a half day or day off. I communicated mainly via SIP phone, IRC, and email with my cofounder and both of us understood when the other needed some time to decompress. The thing was, working for ourselves building something we wanted to exist, we didn't need much time for decompression. I made enough off that business to be debt-free (from a starting point of about -140K USD), build up savings and retirement accounts I ignored before, and coast for the next 18 months doing whatever I felt like (which was a self-directed study of computer science and a lot of Magic: the Gathering). I didn't get rich, but I did improve my situation substantially. If I didn't have commitments to my family, I would jump at a chance to do something like this again.