I use dimmers as well. On the weekend I'll go into the reptile room around 1 PM when it will be it's absolute warmest. I will then bump the dimmers to the max temp that I want the hot spot to be. That should ensure the temps don't go crazy. I also check them twice a day and changed them if needed, but using this method has made me not have to adjust it so much. When I first started using the dimmers, it seemed that every time I went into the room I would play with the temp. It became very frustrating. Thermostats are in my future!