Unless you're running it on Propane or some other kind of "dry" fuel, don't worry about hardened seats. Back when the swap to low-lead and no-lead fuel first happened, we had some problems with exhaust valve seat erosion, but for some reason it hasn't happened much lately. Maybe they changed the fuel blend in some way.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!