Legally I have had one employer contract call out that they expect you to work for certain hours, but that was a Canadian startup; none of the American companies have had that I remember.

Ethically though, I don't feel this way at all. They're paying for my output not my time. I don't get paid overtime when I work extra nor do I get credit for working on the weekend.

I don't think I'll convince you but I guess I would say you don't owe your employer your life. They'll cut you off when it's to their benefit and it's best you do what's best for you.