At this point, I doubt anyone has actually owns a CD-R that has deteriorated. I have seen some specifications that CD-R media that is kept on a shelf is supposed to last from 15-20 years without any ill effects. Any time past this does not mean that the entire disk goes bad all at once -- it just means that some parts of the readable surface of the disk may become hard or impossible to read.

It depends on the quality of the recorder, the quality of the optical media, and the speed at which the recording is made. Recording at higher speeds can mean that the recording process is carried out at or very near to the accuracy limits of the drive. The closer the recorder operates to its limits, the greater the possibility that the disk contains borderline or real errors, correctable or non-correctable. If the laser in the recorder is dirty, the possibility of a borderline recording also increases. Cheap media is generally of lower quality, again increasing the risk of producing a borderline recording. It is highly recommended that you purchase quality media and refrain from recording at high speed, even if the media and recorder both claim it possible. I have been creating CDs for about ten years now and I have seen optical data disks become unreadable in as little as *one* year. Some work fine after ten years. I can say that the average quality of the media has probably declined, as there are more and more budget products on the market, some with borderline performance. It is also recommended that you test the recording by readings its entire contents, both in the drive it was created on and in a different drive. The second drive will be slightly different mechanically - a disk that works on one may not work on the other. Only after I have made *two* reliable copies, do I consider it time to delete the source data. One of the copies is placed in storage and is not touched unless the other fails.