It appears that a RoadRunner DHCP lease is good for about 2-3 days at a time, and it seems to be renewed automatically to the same IP unless you change to a different NIC. I have been swapping between an NT gateway and a Linux gateway several times in the last 2-3 weeks, and they always come back to the same IP that they had based on the NIC. The delta has been 1-2 days on the switch. I have been using the Linux gateway exclusively for the last 6 days, and checking the NT event log shows that it didn't even try to renew the lease for 2 days after being disconnected.