Back when hard disks were expensive and CD-R(W) discs (relatively) cheap, I used to do backups and move less used stuff to CD's. A number of years later when this was no longer true (and CD's were becoming laughably small) I moved all the data back to hard drives. In the process I discovered that a fairly large fraction of the discs had developed some minor corruption. Luckily I was able to recover the vast majority thanks to GNU ddrescue ( https://www.gnu.org/software/ddrescue/ ).

The bottom line is that for long term preservation you really need to keep multiple copies, preferably on multiple mediums, and regularly check and recopy them before the medium gets so obsolete you can no longer access it.

(Yes, I realize the article touches factory pressed discs rather than CD-R's although there is a short mention of such discs too)

It's kind of like RAID for data, and removes the uncertainty that maybe ddrescue wouldn't get an I/O error and just receive and save bad data (it happens). It'd also be capable of repairing damage, up to the redundancy level par2 archives are created at (default is 5%, can go all the way to 100% -- which would mean you don't need any of the original data assuming all par2 files are not corrupt either (which it can also handle...)).