I suspect failure is more or less random. I have a mix of cards, some 5 years old, youngest 2 years old. Admittedly, the very oldest and smallest got relegated to the Sigma Merrills, which are used only for landscape / still life, so the lengthy write time is irrelevant. (the cameras are on tripod on a time delay anyway - why o why wouldn't Sigma have a remote release shutter port?)