75 to 78 ambient isn't bad and if that can be maintained year round (even in the Winter) it wouldn't be horrible. It is just a little low of optimal or a match for their natural habitat temps. If you are keeping you snakes in a seperate room, many people will get those oil space heaters and bump the room temp up closer to 80. You can put it on a thermostat and since you ambient is already in the mid 70's it wouldn't have to run to hard to make up the difference. Hope that helps.