You are paying your balances every month, so it does not really sound like you have to worry. When buying a home,I canceled several unused cards. My loan agent told me the only thing that could raise my score (it is very high already), would be to NOT pay off my cards every month, and carry a small balance in at least three different accounts. You will have a different score with each of the three agencies, and it is not like a few points will generally make or break a decision to extend credit.

The main reason I close un-used cards is that I tend to get hit by fraud alot, and it is easier to keep tabs on less cards.