Of course not. The whole reason many of us became entrepreneurs in the first place is to minimize the amount we have to work.
I, for instance, spend maybe five hours a week maintaining the little web empire that's bringing in enough to live comfortably on. Sure, there's always a period of intense building at the beginning of a project where you can find ways to occupy yourself for upwards of 40 hours in a single week, but if you choose your niche well that period doesn't last long, and soon you're on to the marketing phase which is measured more in calendar time than IDE time.
Naturally, if you're the sort of person who works 80 hour weeks, you'll find a way to build a business that requires 80 hours of your time each week to stay out of crisis. On the flip side, if you're the sort of person who prefers month-long periods of idleness on tropical beaches with occasional email checks to verify that your business is still running itself, that's entirely doable as well.