365 Guido? So are you saying that you don't brumate?

Well, the reason I replied to the OP (not that he'll ever read this) that a heat pad on 24/7 is excessive is because I live relatively near his locale (Essex County, MA) and I know that summertime temps between sunrise and mid-afternoon there can fluctuate by ~50 degrees Fahrenheit. And, the OP states that the snakes are WC. So, hundreds of generations of his snake's ancestors have become habituated to nightly temperature fluctuations to the point where it is now needed for optimal health.

Now, if he had stated that they were WC from Florida, or that they were not WC but were, for example, F7's, F8's, etc, which more than likely would have been slowly weaned off temperature fluctuations then my reply would have been different.

I tend to believe that wild northern Garters undergo a "mini-brumation" most summer nights, when their metabolism slows down substantially (July heat waves are the exception to this). And that this is beneficial to them (yes, even with a lump of a meal in their midsection). Their engines were not designed for 6th gear all summer long. They are not Ball Pythons or Boas or another tropical species and require very different care.

I learned this the hard way.