Are copper plugs better but don't last as long as Iridiums?
no, that is a misconception made by ill advised people.
iridiums are better but are a lot more expensive, if the iridium plug gets blon out u need a colder heat range plug, the colder the plug the more recessed into the plug the electodes are and the less chance of the spark being blown out.
the copper plugs are just a cheap alternative, you can buy almost 10 sets of copper plugs to the price of 1 set of iridium plugs, but the iridium plugs generally last about 20-30k miles even on tuned engines, (not that long on a raced car though)
also guys how much are the ngk iridium heat range 7 plugs for delivered thanks