The Platinum plugs in my Ford Ranger are good for 100,000mi. as are most new engine applications. (You wouldn't want to leave them in that long 'cause you'd have a devil of a time removing them) The new electronic ignition systems plus the exotic electrode materials make for great plug life. Even an old massive electrode plug will last 15-20k with electronic ignition.

You're right about the hype for spark plugs. If your ignition system is in good shape any (recommended) plug will do. If your system is getting a little weak exotic electrodes may help. Multi electrodes extend the life of the spark gap as they present more surface area for the spark to errode. The spark can only jump to the single closest point. As that point errodes, the spark chooses the next closest point. One spark at a time. No matter how many electrodes there are. Splitfires are big on the hype.