I echo the sentiment that you must consider what you are actually willing to spend for the room. There are countless places where if I counted the retail rate of the hotel I get some ridiculus cents per point. But that does not really reflect the real value because there are always deals to be found somewhere else.

I value my points at the following and almost everyone on Ft will say my values are low.

HH=0.5
Marriott=0.75
Hyatt=1.1
SPG=1.8

Even with such low values I tend to find some other method of booking which is cheaper 8 out of ten times. It might be priceline, some other hotel, some hotel promotion or something else.