I had yellows in my mustang until I blew one out (a lot of autocross) and went to coil overs; I wasn't running them even close to full stiff. A buddy of mine with a VW ran his at full stiff and blew one out as well. My car isn't a street car any more but I had oranges (STR.T) in a daily driver (SVT Focus) for a while but again they just don't hold up long on the street. There are better options for street driven long term shocks out there then off-the-shelf Koni's IMO.
Did you tell KONI about the failures? What did they say?

I know they're revalved konis.