Since the rule (even if not strictly enforced) is that it is for the length of THIS stay, then I personally would not consider this an exception to the rule.
However, I have a situation coming up which I am thinking about considering an exception. We are doing a split stay in April. April 2-7 at Coronado Springs and April 7-13 at the Grand Floridian. I am thinking about buying a mug at CSR and continuing to use it at the GF. Ya, I know the rule also says "the resort the mug was purchased at", but since since it is a split stay (basically one trip, but spent at two hotels), I am inclined to consider my actions as keeping with the spirit of the rule, even if not strictly the letter of it. It's not like I'm taking it with me to every resort we eat at, or to the parks. I am using it only at the hotel we are staying at (whether CSR on the 6th, or the GF on the 7th) and for the length of that particular trip (albeit, spanned between two hotels). I know that many people will adamately disagree with me, but that's okay. lol