Also, these XPFMs (and the dual load appliance module) are only driving relays with 110V coils, so the load is very light; probably less than 100 mA. I don't expect that it's enough load to damage the contacts (unless possibly the back EMF from the coil is doing it) and I expect that this would be enough wetting current to keep the contacts clean.
BTW, if anyone is curious, these control the speed of ceiling fans. The appliance modules control relays which switch run capacitors in/out of the circuit to vary the motor speed -- 2 appliance modules with 2 states each for a total of 4 states (low, medium, high, off) -- and this design has been working great for years. Smartlabs has since come out with the FanLinc, but IIRC, X10 users only get on/off and no speed control.