All the ones that are failing use either a 3v wall wart or a 12v wall wart. The 3v fountains are cheap ($5-20) and I typically have a handful fail every month.
You said in later post that the wall warts are not failing, so in this quote, you are referring to the pumps, right?
You say you have a number fail (hand full every month) so if it is the pumps failing and not the wall warts I am barking up the wrong tree thinking the X10 module is killing wall warts. Sorry.
My two cents is this. The little three volt pumps use small, cheap DC motors which probably do not have a long life span, especially when damp. The submersible 120V pumps where a sealed coil spins a magnet impeller should last much longer (although I have to clean my two every month or so). Do you have any of the "foggers"? I can't get them to last very long either, even when I use distilled water. (?)
I modified that post for clarity.
I dont have any foggers, but a church I used to work for had a few. I used distilled water and they still failed eventually.