Quick question

I have the bigger version of that one you mentioned. Had it for about a year and never had a problem. They seem to be well constructed. I installed one of those digital probe thermometers and every time I walk by or look at the time, I watch what the little screen to make sure my temp is stable. You should make a habit of that as well. Good observers avoid disasters in this cases.

I wouldn't worry about the heater too much. Just keep an eye on it, as you do with any other thing inside your tank or that is vital to it.