I have always left my warmers on 24-7 and the only thing that has happened to me is the bulb will go out lol. I would put a candle plate or something underneath the electric warmer because I have noticed even with only leaving on for a few hours, sometimes they can get hot and make the counter top, shelf, etc a little warm. I have about 4 different brand melters (Scentsy, BH&G, Levine Gifts, Candlewarmers.com) and have not had any problems with leaving them on all night yet. Now, going thru bulbs is another story lol.