I've had two chins in a row and neither of them spent a lot of time on the chin-chiller. I used to refrigerate them but neither of them liked it cold. My new chin does sleep on it occasionally. Ultimately the chiller doesn't do that much to the animal's core temperature. That is regulated mostly by the ears, which as you can see on a live chin, are loaded with blood vessels. The ambient room temperature is the most important. Typically if the temp is high they will be less active but not always. 70 is a good temperature. 75 is considered the maximum safe temperature you want to keep a chinchilla. I do speak from experience, living in a warmer climate, that some individuals can become accustomed to higher temperatures although it is not good practice to go above 75 and there is a heightened risk of potentially fatal conditions. My first chin was kept in a room that was probably 85-90 degrees during the day before I got him but I am also aware of chins that have actually died at lower temps.