One thing I can say is some CDs from the past are notorious for going bad within a few to couple years (even quicker if used more often). I do have a strange feeling that some CDs were manufactured better than others For instance, we have some very old CDs that are still in remarkable shape. Same doesn't go for very specific CDs (probably low quality) though.

One such CD for instance is Card Crazy (which contains a whole bunch of card games as well as few other games). Within a few years, that CD deteriorated like crazy to the point I can't even back it up properly. Let me put this way, it was having weird problems just 1-2 years after purchase. I have a somewhat backed up ISO and tried to back it up again (as a separate file of course). Sadly, it's beyond repair as it's now even worse.. 😒

Most CDs from our experience (in our household) do stand the test of time though while some end up going bad within a few years.

As far as I know properly cared-for factory pressed CD's last for a yet unknown but very long time, the ones that don't have documented reasons. I know of at least two:

- CD's from the early 90s manufactured by PDO UK (mostly music CDs, but Daedalus Encounter UK PC version springs to mind): due to materials used these discs show 'bronzing', bronze-coloured coffee-stain-like spots in the reflective layer that show up over time, starting on the inner and outer edges. All of these go eventually and become progressively less readable. I have several copies like this in various states of decay.

- 'Clouding' from chemical outgassing of the box or manuals: a milky, misty or spotty layer on the reflective side of the CD that prevents the laser from properly reading the disc. Can be cleaned off if caught early and not even necessarily a problem in it's early stages. Machine-polishing will probably always get it sorted. Conquest Earth PC UK suffers from this.

Then there are jewel cases that grip the center of the disc too tight, hairline-cracking the plastic over time. I think the stories of 'exploding' discs in 50x drives originate there.

DVD's are another story though; depending on the glue used to bind the two polycarbonate halves these might separate or discolour.