At present, stated CD-R lifetimes are only estimates based on accelerated aging tests as the technology has not been in existence long enough to verify the upper range. With proper care it is thought that CD-Rs should be readable one thousand times or more and have a shelf life of several hundred years. Unfortunately, some common practices can reduce shelf life to only one or two years. Therefore, it is important to handle and store CD-Rs properly if you wish to read them more than a year or so later.
Burned CD-Rs suffer from material degradation, just like most writeable media. Optical discs commonly used for burning, such CD-R and CD-RW have a recording surface consisting of a layer of dye that can be modified by heat to store data. The degradation process can result in the data "shifting" on the surface and thus becoming unreadable to the laser beam.
Recommended care and storage practices for archival CD-Rs include:
Store vertically in jewel cases or slim-line cases, one disc to a spindle. Archival cases use a ridged ring which grips the disc and prevents the recording surface from touching the surface of the case.
Avoid bending the disc. To remove a CD-R from a jewel case, press down on the hub while gently gripping the edges of the disc; you should be able to simply lift the disk out of the case.
Always hold a CD-R by lightly gripping the edges of the disc. Try to avoid getting fingerprints on the data side of the disc.
Store in a cool, dry place. Optimal temperature range is 5-20°C (41-68°F). Optimal relative humidity range is 30-50%. These values should not be allowed to change rapidly.
Avoid direct sunlight. Sunlight can heat a jewel case and indirectly thermally stress the disc itself. Direct UV radiation on either side of the disc itself can degrade the dye layer in a CD-R. On the other hand, smaller doses of X-ray radiation, from airport screening for example, and magnetism should not affect a CD-R.
If possible, use only a felt-tip water-based marker to mark the label side of the CD-R. The best place to label a CD-R is the clear inner part near the center. Alcohol-based markers are thought to be less harmful than xylene or toluene-based markers. Typical permanent markers are xylene or toluene based and should never be used to label optical media. Many vendors sell marking pens which are safe to use to label optical storage media. Paper labels should be applied to the outside of the jewel case, not to the label side of the CD-R itself. Over time, solvents in the paper, adhesives and inks can all degrade the disc. Labels applied unevenly to the disc can also cause the CD-R to wobble in high speed players potentially causing read errors and/or destroying the player!
Avoid scratching either side of a CD-R. Perhaps counterintuitively even minor scratches on the label side can damage a disc, as the layer of plastic between the label side and the reflective layer is much thinner than the other side. Because CD-Rs use error-correcting codes, minor scratches on the data side should not render the disc unreadable, unless there are many of them close together. Deep scratches on the data side can interfere with the focus of the laser and render a disc unreadable. Scratches from rim to center are less harmful than concentric circular scratches. Writing on the label side of CD-R with a ballpoint pen can destroy it.
While not water proof, CD-Rs are not greatly affected by exposure to water unless they have inkjet printing on the label side. Water will cause any inkjet printing to run unless it is protected by an outer layer.
Use 650MB or 500MB CD-Rs. CD-Rs with capacities over 650MB achieve their higher capacities by reducing the track width below the minimum values specified in the CD standards, so their long term readability is less well tested.
