Oh I should have thought to mention this. If you go back to using aspen at some point. I've noticed with ours that if you use to deep a layer of aspen it is tougher for the UTH's to get the proper heat up to the snake. Also I've gotten in the habit of finger fluffing the aspen up a couple of times per week, especially inside the hides, as especially as they get bigger the snakes weight compresses it down quite a bit. Anything compressed like that just can't transmit heat as efficiently.
~~Jo~~