Regardless of no warning, only leave your freezy mugs in the freezer for an hour instead of days. It refers to a non-toxic gel in the filling area of the mug, but I think that means less quality. My freezy mug split open after several days. Luckily the interior remained intact so I can still drink my Whiskey Sours with the best of them.
I'm on vacation, can you tell I am bored.