Physical degradation of CD's

I owned a small recording business and would routinely furnish my clients with copies of their performances that were burned with a pro level CD recorder. On rare occasion I would get a complaint of "drop-outs" on the disc.  At first I attributed it to the clients using an inferior machine for playback but I finally traced it back to the discs themselves.  That is when I switched exclusively to "Archival" quality CDs.  The phthalocyanine dye or ink used on these discs is remarkably stable and even extended periods of exposure to sunlight will rarely cause them to default. Since making that switch, I have only had one problematic archival disc and that was one that refused to initialize.  Have I checked every disc I made since then ?  Of course not, but I've received zero reports from clients that the disc performed poorly.  I'm sure that stamping a disc is more reliable than burning a disc but that is what we have available at present.

Well I own over 3,000 cds ,I don't stream.Buying them now for like a buck and that's cd sets also ,box sets to,Crazy.I only buy ones with not scratches. I find people who used a cd player in there cars using  have then scratched like crazy.I found some that need good cleaning with 70% alcohol.Removes growth on them.They play great again.i own 6 cd players. The only trouble I had with one was years ago .I had an Onkyo high priced one .I had bought when cds first came out .It lasted 5 years Tried to get it replaced, but It couldn't be fixed.When I think I used to buy cds for $16 bucks or more or cd box sets for 50,60 bucks ...WOW.

There are a lot of reasons why CDs fail to play correctly.

A case of "CD rot" -- i.e., oxidation of the aluminum layer -- is very, very rare in all but the earliest replicated discs. It can be identified with the naked eye as black layers of oxidation that slowly spread across the metal layer.  The change in reflectivity is what makes the oxidized areas unreadable.

The cause of this is leakage of air onto the surface of that thin layer, usually through physical damage (like extreme flexing) or because of manufacturing QA failures.

If you don’t see black aluminum oxide patches on the reflective surface of a misbehaving disc, there’s a different reason why the CD is not playing correctly.

Much of this, btw, doesn’t apply to recordable CDs -- which use far more sensitive dyes -- and to early DVDs, which are more susceptable to oxidation because of their multi-layered physical construction. It also obviously does not apply to gold CDs, since oxidized gold has the same color and reflectivity as elemental gold.

I can't speak authoritatively to the point, but I'd expect that, barring physical damage, oxidation "rot" is unlikely on any disc manufactured in the last decade or two.