Modern cars typically don’t need plugs changed until 100k. (snip)
The 60,000K recomendation for a plug change is about as far as anyone should go, if they expect the LF4 to perform the way it should.Cadillac recommends replacement at 60,000 miles, but I haven't heard of many that are at or above that mileage. Tuned cars and ones that are tracked would probably benefit from changing them by 60k, or sooner. But you're right that in most cars today they will easily last 100k especially if you use top tier fuel.