What were you doing to them? I treat my Kindle terribly and the only damage its ever had is a small part of the screen which no longer works because my keys pushed into it.
I've got a Paperwhite, so maybe that's what did it. I don't really see the point in the higher end models myself, I wouldn't even have bought the Paperwhite if it weren't for the screen backlight.
I moved to a Kobo Glo HD after that. DRM free, account free, same screen, more robust.