When do you need to reserve a NYC hotel?

I'm planning a trip to NYC for Spring break, and I'm wondering when the best time to reserve my hotel room would be in order to get the best rates and also to ensure that I get a room in the hotel I want? ... My husband and I are going for Christmas and we have reserved a hotel already as the prices are likely to get higher we think. The good thing about reserving a hotel now is that you can cancel it if you find something else which is better later on. Good luck. ...