I was reading an article about something we all know CD / CD-R lifespan is not long enough as we think it should be. Everybody experienced this, recording a CD and after some months / years it doesn’t work.
The author of that article has been creating backups in CDs for some time but now, since hard drives are not that expensive anymore he decided to put all the data in those CDs into hard drives… while doing this he realized some CDs were broken so he wrote down some numbers and more than 10% of the CDs were useless.
In my experience, I have to add, this is not only related to poor CD quality but also to the player itself, the CD-ROM drive.
I have noticed while doing support / maintenance that some CDs only work with some drives. For my surprise the first CD I burned (yeah, I still keep it) is still readable. That says a lot about the quality back then when CDs were expensive. That CD was recorded more than 10 years ago.
Another thing to keep in mind is that if you want your data to be recorded efficiently you need to use a lower speed (not the maximum recommended) since the laser marks the cd much better and the failure rate is reduced.