Most of our E-Z Heat pads come with a thermostat which allows you to keep them plugged in continuously, as long as you fly a couple times a month. The thermostat will come on at 120F and go off at 165F. Therefore it will keep your oil between these two temperatures at all times. The pads that do not come with a thermostat are the 154, 156, 912, and 9.U. These pads do allow you to leave them plugged in overnight without a problem but not more than 24 hours.