Ironically, it looks like I have a card that is showing signs of failing over my last three shoots. What is leading me to think this is that I shoot dual card. My primary card has one or two images that are corrupted, however my slot two card does not have the corrupted images.
That being said, I've never had a card failure until apparently now.
However, my second slot card has saved me from mistakes that I've made. Since we're all human, we are prone to making mistakes. I think that's the biggest advantage to having a second card.
Also, I've never been in a car accident, yet I always wear my seat belt. I've never had my house catch fire, yet I carry fire insurance and have a couple fire extinguisher handy. I haven't had an unexpected flat tire on my car in a couple decades, yet I always have a spare tire. Etc.