My house is 30 years old and the same circuit that feeds "all" of the bathrooms also feeds the garage. Amazingly, the only problems occur when someone uses a hair dryer along with the Christmas lights (not too often). Either put the GFI in the breaker panel or go through the effort of finding the first outlet (which I did) and put the GFI there (assuming it's easily accessible). Will open if you accidentally step on a Christmas light. Break up the circuit if not too difficult.