Interesting, David. I have literally thousands of CDs and cannot think of an instance where one of my commercially produced CDs has "gone bad". I don't know if that's because I keep them in clean, dry areas and don't subject them to use in the cars or sliding them in and out of binder-type storage albums or just luck on my part.
Even CDRs I've recorded over the years have had a remarkably low failure rate, and those that did almost all were used in the car and subject to high temps in the summer. My CDRs are mostly to archive more than a thousand Grateful Dead concerts and other recordist-friendly performers, from the old tape-trading days up through the digital file swapping hey-day.
I'm with
@godofwealth on this and don't disagree with you either David about multiple back-ups. By far the majority of my failures have been from media such as hard drives and SSDs. Unfortunately, including several laptop computers. At least I had the foresight to make sure that enclosures I bought for drives had both firewire *and* USB, since firewire is scarely a thing anymore. I too have a bunch of zip drive media and orphaned SCSI drives in the junk drawer.
Steve Z