Some times we give them more credit than they are due for knowing what they need. If they truly knew what was best I'd never have a snake go off feed when its young or try and escape.

The truth is that yes they may thermo regulate when the temps are cooler but the fact remains that it might not be the best thing for them. I have some snakes that never leave the heat and some that never leave the cool side. Since I know that my temps are such that they can hang out on either side and not suffer any ill effect I don't worry. But if my temps were not with in the range of their optimal range to sustain a healthy active immune system then I would worry.

Just because I snake stays in an area that is cooler than what is normally offered doesn't mean its good for it. It just means that it is reacting to an environment that it has been given as it normally would with out thought of the possible out come. Thats where we as keeps come in it is out job to make sure these animals are given an environment that do not lend them selves to avoidable problems.

Again just my point of view from my limited experiance