You women know who you are. You treat them rough; you use them often. As a result, they break frequently and thus require frequent replacements. I wish to invent: The Everlasting Nob Slopper.
Wiring wouldn't be any help, they don't feel any of the wear. Better soldering, perhaps. The motors are made of plastic, and are limited in material weight by the battery's limited power.
Fuel cell vibrators? Made out of titanium instead of plastic? Soft plastic/rubber outside?