In signal-level service, the Kitfox switch would probably outlast the airplane. I obviously have no first-hand experience with a failed Kitfox trim switch, but my guess is that the problem with it is contact wear related to back-EMF from the motor. Since the switch has to operate the motor in both directions, it's not possible to protect its contacts with a diode across the motor like you normally would. Either orientation of the diode would short the drive current in one direction or the other. It's not really a problem with the switch Kitfox selected; it just lives a particularly hard life.