Fortunately, 100+ octane racing gas still has enough lead additives in it to do plug readings after a few hot laps. I used to go to the track with 4 or 5 sets of plugs, and we might use all of them while tinkering with mixture settings during practice. A quick trip through the glass bead blaster got them ready for the next week's racing. With a good hot spark ignition system, plugs seldom "wore out"- - - -they just got dirty enough to need a cleaning if the mixture was a little off.
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!