Didn't realise they lasted longer than normal copper tip.
As suggested they won't offer any noticeable improvement over a well set up ignition system with standard plugs. They will offer an easier start though when the chips are down in cold damp conditions. This because the exotic material allows a finer tip, in turn allowing spark to jump more freely hence with lower voltage. Gold palladium was first used for fine tip plugs now it's Iridium.
Have just put one in my Velocette and managed to start it before my leg gave out, so that's an improvement
