An unregulated UTH will hit the 120 degree mark in under 45 minutes AND KEEP CLIMBING. I tested one, and unplugged it after it hit 147. It took under an hour. No amount of aspen is going to protect against that. You know the saying about how to boil a frog? If you put it into boiling water, it struggles to get out. If you put it in tepid water and slowly bring the water to a boil, it never realizes what's happening and it dies. Same thing with snakes. If the pet store let you walk out with a new snake, UTH, and no thermostat, AND NEVER COUNSELLED YOU TO GET A THERMOSTAT, but they sent you out the door with everything g else, right down to 2 hides (good) and a lamp (unnecessary), then shame on them. Maybe they just didn't have one to sell you...