The bulbs, if left on should remain about the same. You have to take into consideration the drop in the room temps too. (especially for those that keep their houses cool) Night drops are not necessary and not recommend, except for those breeding. Temps should never drop below 80, on a normal basis. Otherwise you are just asking for a respiratory infection. The other thing with bulbs, is that they suck out the humidity. They're terrible on your humidity. It's a matter of seeing what works for you, and remember if you decide on a bulb ALWAYS have a spare.