I had a 6-hour wait in BWI September 12, 2005 before my flight on a different ticket and asked about having my luggage forwarded on the different ticket. The CSR went to check w/her supervisor and came back with the info that if the time between the different-ticketed flights had been less than 4 hours, they would have done the transfer, but were not able to do it because the time difference exceeded 4 hours.