I really don't get the point of doing that. There's indeed a limit on how much you can "carry over" in most companies, but not in the one I work. I've been there for over 10 years. I will eventually take a very long vacation, perhaps 3 or even 6 months. So I am slowly building up (I might take some unpaid time off if I need to) towards that. The idea is to do a kind of sabatical... I've lived in 3 countries so far, and I would like to spend time actually "living" in one of them again, not just visiting for a few weeks. I don't feel like I am doing "overtime" in any way, and my company is getting value from every working hour I put in, I can tell you that.