I see some references to family throughout the comments, but one fundamental thing is that things are different once you have a family. The founder of our startup always goes home to have dinner w/ his wife and kids, but it would be a complete mistake to say he's slacking -- he works late into the night from home.

Steve Blank wrote a great post about how to navigate this tricky balance of startup/family and what worked for him. It's here: http://steveblank.com/2009/06/18/epitaph-for-an-entrepreneur...