First off..... measure the thickness of that button with a good set of calipers. I'd then lap it with some vey fine emery on a piece of glass to get rid of the pitting. If left as is, that pitting will develop hot spots on the head and piston and increase your engine temps. When the pitting is gone, measure the thickness again. Subtract the difference and add appropriate shims to get back to your starting point. You'll probably only remove 0.1mm after lapping. That means your engine will always need 0.1mm more shimming than one that hasn't been touched.

Next, use a piece of 0.040" or thicker resin core solder (easier to compress than solid core) with the engine assembled. Make a small "L" shaped bend in it and insert it in the plug hole so it faces the area where the piston will compress it against the button. Turn the engine over ONCE and remove the solder. Measure where the piston has flattened the solder. Try to get the shim stack so you have 0.028"- 0.032" head clearance on the engine. On a stock 35+21 engine I normally have 0.8mm of shims (adding 0.10" to what it comes with) to get 0.030" head clearance with a Nova C7TGF plug running 20% Byrons. I have not seen any detonation running at sea level in FL in 90F+ temps with the engine @ ~260F after a good run.

I pull the plug after every run and inspect it with an eye loop. If it looks sanded or pitted- its gone. Slightly shiny and silver/tan is great if you're making good power. Dull silver/tan is good, but keep an eye on it as the weather changes. It takes a good 5-10 minutes of racing on a new plug to read it. Big races get a new plug before every main- usually replaced before "happy hour" so I can read it and check my tune.....I don't spend $500 to travel to end my main with an old nasty plug. If I ever "pop" a plug I set the engine aside to look at later- it usually needs a rod.

These things don't take care of themselves.... you have to keep on top of a ~$600 investment. A $9 plug is cheap compared to popping a plug element in your engine. 99% of the time if you lose an element you gouge the piston/sleeve. If you can find some Ninja/GRP plugs they will last at 300F+ if you happen to mis-tune for a race.

To me, a properly broken-in and maintained engine is worth more than a new one.....$25 in fuel plus hours of time count for a lot.