I have my old Silver and Blue cards attached to various suitcases, laptop bags, and carry-on backpacks, some of them slid inside Hard Rock Cafe protectors, simply because the membership number is always current. My faith in human nature being such that a Good Samaritan coming into possession of my lost bags can ring the BAEC and they can reunite me with my things.
Despite snappages and losses, I still have a few left to call upon for future travels, and I can always request two replacement sets per year, FOC.