If you are on your original battery you are most likely correct, a battery lasting almost 5 years is a good thing but likely to be the cuase of your lack of starting.

There have been starter issues but my money would be on the battery as well.

Most auto parts stores will check the battery for free and let you know if it needs replaced. Wal-Mart has good prices and many after market battries will work inthe space provided for the Commander as the rack is enormous. I have a yellow top in there now.