"I would say they are so good, buy 2, but I don't think you will need to replace the first for a long time. I read in one review that this heat source can only be used with a zoo med socket, NOT TRUE! I have mine (150W) in a Fluckers light fixture. As long as the fixture has a ceramic base(No plastic), is rated for the wattage you are using (or higher), and is safe to use with ceramic heat sources, it will work just fine. I went thru a red bulb in about 1 month, then it burned out. Waste of money. This keeps my litte Bearded warm and happy. By the way, his name is Fluffy."