[eli_gottlieb]

The real question is of marginal productivity-per-hour. We know that work-hours have a diminishing-returns point passed somewhere around 30-50 (depending on the person and the occupation and the match between them). I think of it this way: if you really need to work more hours to get more done, only keep doing it as long as your productivity-per-hour stays the same. That's the point where you're making a zero-sum trade of more hours for more stuff done.

However, there's also another really important aspect! If you only ever focus on working harder, anyone who works smarter can come along and beat you while working less than you. Beating them through sheer work-ethic will easily push you into negative returns-per-hour, destroying you and your business through sheer desperation.

For example, anyone with a source-control tool will be several times more productive in software engineering than someone who didn't use one and has to manually revert his changes. Remember, this used to actually happen.

So when you're working hard overtime, watch your back! You could be competing against someone cleverer than yourself.