I have a 20 gallon tank that I got off a friend in 1990. Came with an AquaClear mini HOB and a PennPlax heater. (had to check what Brand) I have moved countless times in that span of 17 years and have had this tank running almost the whole time. Maybe 2 years where it was not running, and both of these pieces are working as well as the day I got them.
I am actually quite shocked that the heater still works, it being one of those cheap kit pieces.