Turns on for about 10-20 minutes, then turns off automatically for about 20-30 minutes, then turns on again, repeat this process over and over again. How long it burns depends on your chance or luck. I bought from two different sellers (two different models) but you can see they are exactly the same and I think they are actually made by the same manufacturer (you know who!). In the product information part they never mention this fact. I haven't returned them, just make sure you don't use them for more than 10 minutes.