Spark Plugs.
At my 14.500 mile service, I had already bought a set of NGK iridiun spark plugs, and removed the original Denso Iridium and put the NGK ones in.
I cleaned and gapped them at 31k miles, and have just replaced the NGK's with the original Denso ones I removed at 14.500 miles, and this at 60k miles.
These plugs are damn good, and I now have the NGK's in store for future use.
Crazyhorse