it depends on what youre hitting, and what youre doing, to be honest. boxes wont do quite as much damage as rails, but theyll still round edges pretty good. if youre gonna be busting out the disasters, youre in for some cracked edges.
my 04-05 karmas (black & red 177) have been holding up like champs. and if you find that they seem super stiff at first, it's alright you'll come to love them by the end of the season