The recording is made in the dye layer, a chemical change, and the dye degrades (particularly in sunlight) so the discs have a limited shelf life. Checking Wiki

The recording is made in the dye layer, a chemical change, and the dye degrades (particularly in sunlight) so the discs have a limited shelf life. Checking Wikipedia, it appears azo dye formulations can be good for tens of years. Melting polycarbonate would call for an absurdly powerful laser, a glacial pace, or both, and you wouldn't have to use dye at all. I'd guess such a scheme would be extremely durable, though.