Equipment failure

I have heard that CF cards can fail for no apparent reason, and that the results can be very frustrating. I has never happened to me until now. Yesterday, an UDMA 7 card failed after an hour of shooting (nothing very intense, just a family walk around town). The card has never left the camera: it just stopped responding at a certain time, and could not be either formatted in the camera or accessed through a card reader afterwards.

This is not a big problem in the sense that could have been worse (e.g. I could have lost images from a professional assignment), but it is definitely frustrating. I guess, the dual CF slots and the option to write files on two cards simultaneously in my Canon EOS-1D X are there for this kind of eventuality.

I will check off this accident as a learning experience: I rarely reach the full capacity of both cards that could be put in the slots, but losing images even once is not a pleasant experience.