Decided to pull the spark plugs after haven been in for 24K. This is in a 1994 Fleetwood Southwind Storm 28ft 454 w/4L80E Surprisingly they looked very good after 24k miles.... https://www.irv2....
Modern spark plugs are rated for 100K or more.. This is due to the metal used in the tips. Of course to get 100K out of 'em, you need a good engine, oil burners kill plugs fast. Bad air/fuel mix can do it too. But the proper plug in a well tuned and properly operating engine should go 100K or more.
6 of mine lasted 15 years the other two had "External damage" (Rodents v/s wires mandated the replacement of 2 plugs)