I wouldn't worry about it. Its not really necessary to leave it plugged in all night though. You can go to any Radio Shack or similar store and get a timer. When you plug it in it won't push any power to the heater until the time you specify. I did this for a while when it got colder here and worked great. I usually set it to turn on about 1 hour before I had to go anywhere.
-R. J.