Patrick McFarland,goes into great detail on CD/DVD media over at the Ad Terras Per Aspera site.
From the article: Unlike pressed CDs/DVDs, burnt CDs/DVDs can eventually fade, due to five things that affect the quality of CD media: sealing method, reflective layer, organic dye makeup, where it was manufactured, and your storage practices (please keep all media out of direct sunlight, in a nice cool dry dark place, in acid-free plastic containers; this will triple the lifetime of any media). More …