Those were put in about 45,000 miles ago by the Pontiac Dealer who did the UIM/LIM gasket replacement in 2003. Funny thing is, my car has always run smooth as silk and with great gas mileage. Just ask Don...mine runs smoother than his. And I (typically)don't replace plugs, wires, or other parts unless there is a problem or maintenance time is due.
On the other hand, when we pulled those plugs, the platinum tips were already burnt down below the porcelain...though they still worked fine...
Now there are NGK TR55s in there and all'* well.
Mike: 1997 SE w/ 183K, aka White Horse
, Gutted Airbox w/K&N, drilled 180* t-stat, tint all around, clear corners w/SilverStars, "PONTIAC" light up tail, PEMs, NGK TR55s