I have a heating pad on one side and the ambient temp. is usually fairly constant. when they do drop i do use a heat lamp, centered over the cage, to raise them. if u do use one over the cool side at night, i would suggest a low wattage bulb bcause at night he temp. only needs to be from 75-80. heat pads work well and they can be left on 24 hours a day with a proper thermostat and ventilation. With heat lamps, u cant forget to leave it on for only 12 hours and have to remember to turn it off. i had a bearded and forgot to shut it off one night and it didnt eat for 3 weeks. not absolutely gonna happen, but it is possible. But if thats wat u want, to each his own and just remember that your snakes health is wat its all about