i'd never be comfortable leaving my snake unattended. if i know i'm gonna be out for more then a few hours doing errands i try to check & record temps & humidity first. i write everything down in a notebook. sounds neurotic i know but i can rest easy knowing i'm keeping everything logged for future reference if needed.
i couldn't live with myself if something happened to my snake during my absence where things were not being closely monitored and something happened like a short in the thermostat that resulted in the heat pad overheating and burning my snake or worse shutting down altogether and resulting in my snake dying from lack of heat.
in the case of an extended absence i'd leave my snake with someone with lots of snake-keeping experience (which where i live i'm almost sure to find no one willing or knowledgeable enough to care for my snake).