Right now, being "between jobs", I get to spend 8-10 hours a day, and I'm lovin it! Being new to knifemaking, I need that amount of time to get anything done. I'm not looking forward to becoming employed again, as then I'll be struggling to find time, too.
A habit I developed several years ago (while trying to complete a personal project while maintaining job and family commitments) is to get up early in the morning, at least 3 hours before the rest of the family, and do my work then. That way, my work gets me when I'm fresh, and there are no competing responsibilities. I found it too difficult to work up motivation after a long day at the office, and I felt that after-work hours should be spent with the family. So...when employed, I get up at 4am, work till 7am, help get the kids fed and of to school, go to work, come home, hang with the family, and go to bed at the same time the kids do (9pm). When I really have a lot to get done, I may get up at 3am for a week or to. If only a person didn't need to sleep!