Your credit score rises with the length of time you’ve had each card, and the amount of unused credit.

Switching cards to get the next 0% deal is not so good, because now you’ve got a new card without a history. Closing an old card is not good either, because you lose the established card that has a history.

Having $20K of credit, with only $2K on it, is actually good. This example shows that you have a high credit limit, but are using only a little bit.

I am writing this off the cuff, based on what I remember reading recently, so please don’t quote me exactly on this stuff. I wanted to point out the nuances of having established cards that are spent much below the limit.