I just installed my new plugs at 47,000 miles. I used a torque wrench, as I have a tendency to overtighten things. the insulators had a nice golden hue. There was some carbon buildup at the bottom of the threads. The gaps were a little larger, but nothing out of the ordinary. I always use anti-seize.
I have to say the engine no longer vibrates at 1900 rpm !!! and feels peppier.