i have ngk also but not iridiums.... i heard of people melting them after spending 10 bucks a piece for them,if those are iridiums
10 bucks a plugs is too much money my ngk tr55'sor tr5 or something like that.. thats how long its been since i had to change them,cant even remember which ones lol,they are doing well i think are just fine!! for a dollar something