What kills recorded optical disks:
1. POOR HANDLING. Even small scratches on the bottom surface (where it is read from) can cause skips and/or data loss, and small scratches on the top can expose the dye layer to air and moisture. Disks should go from their case into the player and back while being gripped only by the edges and the center hole. Disks should not be set down, or stored in sleeves that make contact with the disk surface.
2. Sunlight. The dye layer on a recordable disk is very vulnerable to heat and ultraviolet radiation, which will break down the dye and make the disk unreadable.
3. Poor quality media. Manufacturers' quality varies a lot, and most of the "brand names" source their disks from other sources, and aren't necessarily consistant with their source. For example, a TDK disk that you buy today may come from a totally different plant than one you buy next month. The best solution is to buy in bulk from the top manufacturers (Google!).
-Troy