I tip at every hotel I stay at. I also tip daily so that the person that cleaned my room most likely will get the tip. If you wait until the end of your trip the maid that cleaned your room most days may not get the tip.
Yeah, we tip usually a couple dollars a service rather it be the bell-hop, valet, or housekeeping. There have been a few times when we didn't leave anything but that was in cases that service was just terrible.
For good service, we always tip the mouse keeper, dining servers, valet service. It always comes back to rewarding yourself with good service in the long term.