I had a Delaware EZ-Pass for a long time and kept it after we moved to Virginia. All of a sudden I started getting dinged for non-payment of tolls even though I had the EZ pass transponder and my account was current. Turns out the transponder died - they do give out after a certain number of years. So I returned the Delaware transponder and got a credit for the funds remaining on it, and opened a Virginia EZ Pass account.