Vibrating Butt Plugs?

I own two of these, produced by different manufacturers, and I don’t use them that frequently… perhaps once or twice a week… Both seem to have failed; they no longer vibrate regardless of the batteries. One is waterproof but only vibrates when squeezed quite hard in my hand, while the other is inflatable and simply refuses to work at all… Is this a common issue, or can I do something to stop it?