I find DVDs mostly pointless now. I've started seeing some from around 2000 which are now unplayable.
Now though all blu rays are inorganic and should last about 100 years. Some can last closer to 1000 years.
But read-only media has always been pressed and then vacuum coated with aluminum. No dyes.
And the main component for both is always polycarbonate, which is organic, and probably won't last 100 years. There were some problems with early DVDs where the polycarbonate was not sealed propery, which led to oxydization of the aluminum layer, that's probably what GP observed. And of course that can happen through degradation as well.
In theory, it's possible to make these discs from glass, which should indeed last thousands of years. I've even heard that some glass music CDs were made for Hifi enthusiasts in Japan.
The funny thing is... The rumor is that M-disc and normal discs are basically the same now. They're made on the same line and labelled differently from what I've been told. I can't vouch for it, but it makes sense and I've seen some folks online posted various test results that seem to back that up. The fancy Japanese certified archival discs are the same way. They're made on the same lines, just maybe examined a bit more carefully before packing.
I hadn't heard about those glass discs! Very cool. Now I kind of want one.
The disc goes into a big case logic cd case, and the digital file gets backed up to two other places so there's almost an infinitesimally small chance I lose access to the content.