Going back through his old CD-Rs and transferring the data to hard disk, Adrian Wong of TechARP experienced a failure rate of nearly 10% for discs recorded some 7 to 9 years ago and kept under ideal storage conditions (cool, dark and dry).
Of the corrupted CD-Rs, many of them only had a few files corrupted, but two of the CD-Rs were completely unreadable. Neither one of the two CD/DVD drives we used could even recognize the CD-Rs, much less read anything off them.
There doesn't seem to be any particular pattern with the disc failures - either with age or with brand. The newest (2002) discs had the highest level of corruptions, followed by the oldest (2000). Of course, those two vintages had the fewest number of samples and the actual results may change radically with a larger sample size.
Even though branded CD-Rs from the likes of Kodak were expected to last longer, they appeared equally susceptible to failure as the cheap, no-brand CD-Rs.
I decided to check through my old CD-Rs. Oddly enough, after checking some 120 discs, I've yet to find a single corrupted disc. I'm not saying that I don't have dead discs, but it would seem that my failure rate for a random selection is less than 10%.
The difference in experiences? No idea. I always buy good-quality discs and avoid no-name CD-Rs (and DVDs for that matter). I always verify the disc after burning too, which does usually catch a few duds before I put them back in the jewel case. Maybe that's the critical factor.
Either way, I now rarely burn discs, CD-Rs or DVDs, having moved to flash drives.
If you do come across a dead disc then Elprime's Media Recovery software might be the tool to save your data.
What's your failure rate like?