Some CD-Rs will certainly be readable after 30 years, but there have been plenty of bad CD-Rs that have become unreadable after less than 10 years.
I had several hundred CD-Rs. Most of them were OK, especially the gold archival CD-Rs from Kodak, so I have migrated the data from them mostly to save space and improve access speed, not for them being too old. Nevertheless there have been a few that have gone bad, but I had duplicates for all of them, so I did not lose the data. Had I not been cautious, I would have lost some of the data.
The main problem of optical discs is their much too low capacity in comparison with magnetic media. A small suitcase with tape cartridges contains as much data as a big cabinet full of the most dense optical discs.
I had several hundred CD-Rs. Most of them were OK, especially the gold archival CD-Rs from Kodak, so I have migrated the data from them mostly to save space and improve access speed, not for them being too old. Nevertheless there have been a few that have gone bad, but I had duplicates for all of them, so I did not lose the data. Had I not been cautious, I would have lost some of the data.
The main problem of optical discs is their much too low capacity in comparison with magnetic media. A small suitcase with tape cartridges contains as much data as a big cabinet full of the most dense optical discs.