During the last three years I have been doing two week stints at a Hilton Garden Inn. Several times, on the weekend I was checked into the hotel, I would take a side trip elsewhere and check into another Hilton (the Waldorf=Astoria once) or other hotel chain while retaining my Garden Inn room. I never had any problems getting credit for both rooms, even when they were both Hiltons. I also never had any problems having two Avis cars rented at the sametime in different cities during some of these trips.