[GarterGuy]

I keep my garters (only garter right now), at the mid 70's with a basking site at around the mid 80's. Yeh, snakes will be slower at lower temps. They pretty much run off of solar power, if you will, so the colder they are the slower they'll be. I wouldn't recomend keeping them cooler, just to make them easier to handle.....better to have a spastic healthy snake then a calm sick one.
Roy

PS....Too warm a temps. could lead to hyperactive behavior.....make sure your snakes are able to regulate what temp. they are. The whole tank shouldn't be heated. The snake should be able to go to warm or cool sections of the tank at will, and also should be able to cool off at night.