I have yet to see a set of platinum plugs go 100,000miles. I've changed them at 60,000miles and they were that shot the car was actually missing under load. I've always run ngk's in my stuff too. My old snowmobile loved the iridium plugs.
SOLD-08 Unlimited X, "jeep green", auto, limited slip, hushpower muffler, Aerotech Interceptor gauge,Powerstroke tranny cooler, skidrow evap skid, AFE Pro 7 filter, Teraflex leveling kit, EVO control arm skids, 15x8 Black Rock 909's, 33" KM2's