Sorry to say but if you're working overtime for absolutely free you're not very smart person.
Granted I am not afraid to get fired so there is no fear involved. However I never got fired in my life.
Should that not happen, I will assume the firm doesn't care if I move on after 2-3 years for opportunities with better compensation.
It is what it is. I'm married and have financial obligations. That said, who's to say I don't moonlight and make extra cash that way? ;-)