Some people use them temporarily as a means to help a snake shed. It is not a permanent solution in many cases because unless the snakes spends a majority of his time in the humid hide, he is not getting the benefit of higher humidity.

Leaving a humid hide in all the time can breed harmful bacteria, fungi, mold. If the snake prefers the humid hide too often, he can develop scale rot and possibly an upper respiratory infection.

If you leave the humidity too low, you risk stuck sheds, and quite possibly a URI.

I found that if you cannot get the temps up with just a UTH, to cover the 3 back sides with house insulation board or cork board. Try to get rid of the ceramic heater or light since it does suck out humidity extremely fast.

You may also have to mist a few times a day. We dont want the substrate too moist, since that can also breed harmful bacteria and promotes belly rot.