Now that the snakes are in separate tanks, I have some heating concerns. Actually, this has little to do with the tanks and everything to do with the fact that instead of being in a bedroom that had A/C controlling the temp, thus necessitating a UTH at all times and hood light at other times, they are now in our living room, which does not have the benefit of A/C (old house, weird construction, the A/C simply doesn't cool the front). This is a problem I didn't foresee in our moving attempt.

For example, it's currently 90 in my living room - dry heat, not humid. That, I would think, means I don't need to be running the UTH, right? But, it will drop down to probably about 70 by morning - it starts cooling rather rapidly after about midnight, which means at that point the UTH should be on, yes?

Considering it takes approx. 4 hours for the UTH to heat up and warm the tanks, how do I run that on a timer? How do I make sure my snakes aren't getting too hot?

They're each in a 29 gal tank with a UTH on one side, water and hide on other side - plenty of room for them to be off the UTH.