My RHM38S fine wire plugs seem to last for ever. For various reasons they have been changed at ~1000hrs but I never saw the slightest wear on them.
Whether they suffer less from lead fouling, is hard to say, because I have not had any fauled plugs since 2005, which was a very inconvenient event at LESO and with no tools to hand. It cleared eventually. I know people who would (and did) depart with a fouled plug.
I can’t see how a spark plug (that is actually working properly) could affect the CHTs.
