The best thing to do is to look at the climate from where the animal is from. For example, animals from the Amazon basin, especially arboreal ones (ATBs, ETBs), experience dramatic fluctuations in the day/night temps. The amazon basin, because of its high humidity, but proximity to the equator, can fluctuate between 90-100 (day) and 60-70 (night). While I don't recommend allowing your herp to drop down to 60 degrees EVER, your amazon snakes, as well as anything from north america (kings, corns, garters, etc.) can probably tolerate a drop down to 72-75 at night. Equatorial or desert animals should be kept at higher temps at all times. Key thing, don't look at care sheets... look at the way they live where they originated.
- Ken LePage