It seems to be a case of archive to CD now, and re-copy at suitable intervals. Presumably 2nd 3rd ...nth generation copies will show some information degradation, but if copies of the initial CDs are re-copied onto top of the range CDs (say) every 10 years then once we get to that century claim we will have copies of the CD's at decade intervals (although it is a logarithmic scale, it would help to re-copy the CDs from decade 2 during decades 3 4 & 5, and likewise the CDs from Decade 3 in decades 4 5 & 6 etc.,).
If this (or something similar) is done then we will be able to identify which discs suffer greater degradation, and the life expectancy of a CD.
Is the recording kept better on the original disc (after 100 years)?
or, Is the 10th gen. copy in better condition ?
Or is the answer somewhere in between, such as the 4th gen. copy (from yr 9) of the copy made in Yr 6, which was a copy of the original CD made in Yr 3 ?
Whatever the answer to this problem, the sooner it is started the better (probably!!!)

Just to qualify that "probably" above, old books and paintings which have been carefully photocopied, patched or 'restored' may sometimes have had a better chance of a long life if they had been kept carefully until today's experts could have a go at them. Although it is unlikely that a single playing of the older forms of recording media (for recording) will cause irretrievable damage.

Nigel