I think spending more than 40 hours per week programming is unproductive, because of the mental exertion, but there's a lot more to launching a successful start

I think spending more than 40 hours per week programming is unproductive, because of the mental exertion, but there's a lot more to launching a successful startup than programming. Once you've expanded to the point where you have people who only program, Joel's advice is probably good: "encourage your staff to work a sane 40 hours per week" except for occasional bursts.