Ummm... on my racing bike I have almost never gotten any flats, so I don't bother to use Kevlar tires. The GT2 tires were no exception, I didn't get any flats. I think I eventually gave one away and another rotted while sitting flat in a leaky shed during the winter (mostly my fault, but perhaps some tires' casings would have survived it).

The Kevlar tires I use on my commuting bike, with which I carry more weight, ride on crummier roads, and--for a while at least--did about twice as much mileage on (when I had a 17 mi RT commute).