Keep Your Credit Accounts Open!
Even if you have paid off a loan or a balance is a good idea to keep your credit accounts open. Closing your accounts has both immediate and long-term effects on your credit scores.
The reason that closing accounts to do with unused cards is a bad idea is because FICO scores take your total available credit into account. For example lets say you had six credit cards and you only really used three all of the time. If you closed the account on the three cards that you did not use that often you will be left with only three card cards. If you are carrying a balance on those cards the FICO score may interpret you as owning less available credit and those cards as being maxed out. This can cause your credit card scores to plunge to the depths!
When in doubt keep that credit account open. This is because the more history of having credit that you have, even unused credit, the higher your credit score will be.
In essence you should always remember that the key to obtaining high credit scores now is to prove that you can manage your credit accounts well over a long time.