Way off topic, but have you actually tried to read them? I was able to get data off some ~25 year old 5.25" C64 diskettes a few months ago, encouraged by success with data recovery from some 3.5" diskettes a few months before that.
Yes, most of them didn't last more than a few years before the bits started falling off. This may partially have been because most of them were SD (720kb) that I'd drilled the HD (1440kb) marker hole into to save money. Worked fine at the time, but probably didn't help boost their longevity.