From myfico.com “Length of Credit History (15% of your score) * Time since accounts opened * Time since accounts opened, by specific type of account * Time since account activity Length of Credit History Tips * If you have been managing credit for a short time, don’t open a lot of new accounts too rapidly. New accounts will lower your average account age, which will have a larger effect on your score if you don’t have a lot of other credit information. Also, rapid account buildup can look risky if you are a new credit user.”