All media deteriorate with time, but five to six years is probably far too pessimistic. Verbatim, for example, claims a 100-year usable life for its writeable CD-R disks. The durability of a CD-R (or recordable DVD) depends primarily on the stability of a layer of dye encased within the plastic disk.
Two types of dye are used in CDs -- one gives it a greenish color, the other more of a gold hue -- but there's no solid evidence that either is longer-lived than the other. All dyes are somewhat light-sensitive, so for longest life, keep your archived disks out of the light, particularly direct sunlight.
At worst, optical media like CD-Rs should last a lot longer than magnetic media such as floppy disks or tape, which become demagnetized and eventually unreadable over time. Commercially produced CDs and DVDs, which do not rely on a dye layer, should last the better part of forever, unless they're physically damaged.
RETIRED FORMATS. Probably a bigger risk for durability than the physical media's deterioration is the potential technological obsolescence of the format. I still have some old 5 1/4-inch floppy disks around and even one or two 8-inch ones. I don't know if any of them are actually readable because I no longer have a drive that can handle them.
The same is true for 78 rpm records, video LaserDiscs, eight-track tapes, and many other now-obsolete storage formats. Archivists say the best way to preserve text is to print with a laser printer on acid-free paper. Properly stored, it should be good for 500 years or so -- provided that people still know how to read then.
Wildstrom is Technology & You columnist for BusinessWeek. You can contact him at email@example.com