Mmario,
Both of the knackered CDs were generally stored in their cases, in a draw, in my house.
Certainly not in direct sunlight or with any massive temperature changes.
Dying after 3 years seems dreadful (and I'm tried them in several machines).
Maybe the technology has moved on in the last few years, but I'm going to be wary of archiving anything long term in this way, until I know better.
Will