Not really. Remember, our cars are AWD, so if one goes, and they are not new, you have to replace all of them
You might be able to get away with shaving down a new tire when the time comes, but that isn't really exact.
I was in the same position, and I asked them if I can cash in all certificates all at once to get all four replaced if I have a blowout or something. The guy said they probably could work something out...but I didn't take their word on it and passed on the certs.