The Dutch PC-Active magazine has done an extensive CD-R quality test. For the test the magazine has taken a look at the readability of discs, thirty different CD-R brands, that were recorded twenty months ago. The results were quite shocking as a lot of the discs simply couldn't be read anymore (spotted at Ars).

I have CDRs (cheap ones) from maybe 6 or 7 years ago.. Still working.

I think it could also be due to the way the disks were stored. If they were in a hot moist environment it could cause the backing to peel away or become unreadable. I am sure there are many factors to why they would go bad, and ways to prevent them.

Personally I don't see how they could go bad if you take care of them and don't throw them around, or set them on your desk and move them, etc. Common sense stuff.

The thing about some of these studies are that they put things in extreme environments to test them, then find they break. Well then they just report that they will break down after xxx amount of time, when in fact 90% of us don't use the tested objects in the fashion their tests were done.