I know that the temps should never go lower 75 degrees at night but is there temperature range that it should absolutely not drop to? I mean like to the point where is could be harmful in any way?

The reason I ask is because my electric bill was higher this month because I usually leave a red bulb on at night so I almost have like a 20 hour light cycle going on. I was going to stop using the night time bulb all together until it starts to get cold outside at night. My room is also the warmest room in the house