Use Permatex Anti-sieze on the threads. Prevents the gaulling that you describe. Even copper-plus will seize in the heads at 12K miles. After having to get the spark plug holes heli-coiled in my VW back in college in the 80’s because of seized plugs that ripped out the threads, I’ve been using it ever since, and have had zero problems with seizing with all my cars and truck since, even my long-lasting Toyota Pick-up that lasted 325,000 miles on a steady diet of copper pluses (NGK) every 12K or my Explorer that is on it’s third set of FoMoCo platinums at 169,000.