[paolomaffei]

You really should have hobbies or you're going to get burned. It is ok to skip it for 2 weeks, maybe even for 4 critical weeks, but don't let "critical" be your startup status all the time. Do yourself a favor and keep your hobby.

[pclark]

This seems rather excessive. Extraordinary results require extraordinary efforts. Saying that, I see no problem taking the odd weekend off or leaving work early to play a round of golf. In moderation. It's easy to slip as have an unproductive month if you have no one working with you.