Lifestyles of the Rewritable and Famous
How many times can you reuse a cd-rw or DVD+RW? How long will my CDs and DVDs last?
Rewritable CDs wear out, but it takes a good long while. According to the Optical Storage Technology Association, a trade group for optical media, a CD-RW can be written approximately 1,000 times before phase change film starts to lose its ability to change and errors accumulate to unacceptable levels. According to manufacturers, DVD+RW disks are also rewritable about 1,000 times.
You can expect unrecorded optical media to stay usable for at least 10 years, subject to environmental conditions.
How long your optical media will last is a more complicated question because it is so strongly influenced by their storage environment. You can expect your CD-ROMs (commercial CDs), recordable and rewritable CDs and DVDs to last for a minimum of 20 years under ideal storage conditions. In fact, under ideal conditions, the record-once and commercially purchased products are expected to last a lot longer than that well past the 100 year mark in the case of the commercial products.
But that's in an ideal environment. Heat, humidity and dirt are the great enemies of all optical media, but especially the recordable and rewritable ones. The film of material that actually records the information degrades when it comes in contact with oxygen. Anything that helps oxygen penetrate the plastic (on the shiny side) or lacquer (on the label side and the edges) shortens the life of CDs and DVDs.
Dirt produces scratches that can thin or penetrate that protection. Heat and humidity can help oxygen seep through the protective layers. All three are bad news. The aluminum recording layer in commercial media is more resistant than the dye used in recordable media or the phasechange material used in rewritable disks, but it also will degrade when exposed to oxygen.
That's why it is not a good idea to leave optical media of all sorts in your car for long periods of time (generally measured in months). Optical media is comfortable in conditions that make you comfortable. Keep it cool and dry and clean and your media will last a lot longer.