As long as your hot spot remaines between 90-93 then you should be fine. Naturally you may need to increase things a little bit if you keep your house colder in the winter but you shouldn't have to add very much. Remember leos need a temperature gradient so hot side, cool side. If you put heat bulbs on BOTH sides you may not get the temperature gradient your leo needs to find a cool spot in case he does get over heated.
I keep a 50 watt blue night light on my hot side along with my uth and it keeps my tank, which is a 20 long, consistantly between 93-95 and my house varies between 60-64 degrees F.