It amazes me how many people in our industry will eagerly work seven days a week without pay for an employer that:
A) Won't do it themselves. B) Can easily afford to pay for it, but won't.
It won't help you get ahead, either. It shows gullibility, not dedication. That's not the kind of quality you want in a leader of anything. It's for this reason I would disagree with your premise that by not allowing yourself to be exploited you're forgoing future career success. You've learned the first lesson in success which is, crassly, don't be a punk.