Not a snarky answer, sincerely:

I keep my heat tape at whatever temp corresponds with the particular animal spending some time on the heat -- especially at times when it makes sense to be on the heat like after eating, when gravid, etc. -- and some time off the heat. If they're thermoregulating in patterns that are understandable, and the measured temps are remotely in the ballpark (so not high enough to be a danger, and not way low), I just watch the animals and tweak a couple degrees as behavior suggests.