So after 120 nights in one year, there is no benefit at all of staying more? I guess I'm at 130 now, so no point in giving Hilton more nights. In fact, I don't need to stay at all next year, and none will rollover until the following year, so I could just take a year off Hilton.

Too bad they didn't allow continuous rollover - if they did, I'd give them another ~30 nights this year.