I kill my heat. With this method, due to the amount of head space and the lack of insulation as I originally protrayed in this thread, I get a few degrees temp loss. I usually do all-grain all the time now, even when using this method, so I don't have the head space problem and I don't experience any loss.
I do not condone ever using an electric burner for temperature correction. It's too sporatic and seemingly impossible to make work correctly. Your best bet is to try and hit your temp the first time and let it hold. You could keep some water boiled and ready to go to add for ramping your heat and some cool water for cooling...this will work to correct temperature much better than applying electric heat. Gas works better, but be aware that the glass thermometer will go nuts when you apply heat and your reading will not be immediately correct.
But, again, a few degrees loss is not a big deal. Still makes fantastic beer.