2 sd cards died in about 15 years. Used like 20 different ones. One card died completely, second switched to read only state, but wrongly reported by other hw. It seems, like data beeing written, but they are not and only older data are there. Yeah, second slot saves lives.
As I don’t like the idea for great photos and finding the one you actually like for composition, pose, smiles, etc… but it could be handy to quickly find the sharpest / blurrest ones. Going throug few thousands of photos from wedding could be a little bit faster. Filter out the bad ones, quickly check the selection, flag them and focus more on the sharp ones.