How long can a hospital wait to send you a bill after service is done?

Question Details:

Local hospital submitted claim to my expired insurance carrier on 01-09-08. The insurance company paid the claim in full even though my policy had termed and my new insurance was in force at the time of service. 2 years and 9 months (09-10) later the previous carrier requested the money back from the hospital and the hospital sent it to them and then sent me the bill. Now my current insurance won't pay it because they have a length of filing expiration of 03-09. Not my fault, not really even the hospital's fault. Is there a length of time that an insurance carrier can request a refund? Important Notice