So, CD-Rs in particular are very bad with regards to stability because the thing you are writing too is a layer of dye. Some are better than others, but basically all will have that dye brake down and fade over time. The type of plastic in the disk as well, a few Japanese disc producers were notorious for using plastic that had a tendency to absorb moisture form the air that would rapidly cause the disks to degrade.

There are other methods of writing though. CD-RWs for instance are much more stable as instead of burning away a bit of volatile dye layer, they are writing to a layer of metal alloy by melting it a little to change it’s crystal structure.

The same is true with recordable blue rays, with Low to High disks using the same sort of dye burning as CD-Rs, High to Low disks use a variety of different mechanisms to write, but some use a similar melty metal as CD-RWs.