Patina. The whole thing will eventually look duller like the spots. Anything that constantly gets heated to high temps will never stay looking pristine. If you are worried about friends thinking you aren't a great housekeeper, then buy an extra set and pop them on when you have people over, but aren't cooking! Better yet, don't invite that type of "friend"!

I've had large gas ranges (DCS and Wolf) for the last 10 years and I am looking forward to my new Wolf induction range and not having to clean all the gas burner components!

I'm sorry to tell you that the caps will get worse and the shiny black finish of the top will also get etches/spots that won't come off. We had a Wolf AG at our former beach house and it was impossible to keep it pristine. I stopped letting it bother me because it was such an awesome cooking machine. Still I think they should use more durable materials. Our Lacanche had a stainless top which looked brand new after 10 years (the brass burner caps were well patina'd though).