Most people choose the wrong time periods for thinking about work/life balance. The usual discussion is about achieving a balance every day or every week. That just dilutes and compromises both your work and the remainder of your life. A startup is a chance to balance out your work and life over many decades. If you can work, say, five times as effectively as other people (which is hard), and if you can get paid for that, you have the possibility to compress your working life into 9 years instead of 45 years--that will give you an extra 36 years with no work commitments at all, free to travel and choose your own interests. Balance in this form can make up for a lot of all-nighters during the startup.