I keep him warm with an undertank heating pad, I don't use a heater lamp. You have to have one warm method. Lamps are usually not recommended for corns, all you need is belly heat and you can get that with UTH pad.
Light is just to keep day/night cycles and "see" the snakes. I have my desk next to my tank, so at night I have a small desk lamp on and that's enough to see the snake.