In my opinion, the real story is that Disney would like for the mugs to be length-of-stay, but they also want to be nice about it, and not have a "mug policeman" standing there checking mugs and turning people away. So they just let people use the older ones if they want to and not say anything. In a business sense, too, it may be more expensive to hire a person to be a "mug policeman" or to implement a way of checking the mugs, than to just purchase more soda syrup or other drink materials, for the extra refills from the older mugs. Just in my personal experience, when I first started purchasing the mugs, I assumed they were for length-of-stay only, and that $10 didn't entitle me to lifetime refills. So I purchase new ones each stay. But I do understand and feel for people who were told by castmembers that the mugs were for lifetime use. My only question is now, that I have a cabinet full of these mugs, when I keep buying more, and run out of storage space for all these mugs, where am I going to put them? LOL