I have a 32gb sandisk and I had no issues until I recorded a big video. After recording this semi long video (4mins), my card was not usable any more after this.
My settings was to save all camera stuff onto the external sd. I think recording a long video might have stressed it out.
I don't know if you guys want to try it, but try recording a long video and tell me if this breaks your sd cards.
Luckily for me, everything is backed up into my dropbox. I just lost that stupid long video.