This is theory, at best. The big audio magazines respond to letter writers
worried about disc longevity about once every two months, and their answer
seems to be that unless something goes wrong in the pressing of the stuff
that covers the actual disc, the disc will last longer than you will live.
I guess the audio magazines could be part of the big conspiracy to take
your $ and then change form factor every 20 years.
I have many discs that are reaching 15 yrs old, and they sound like they
always have.