I read this on
http://www.mscience.com/longev.html#RESULT :
CONCLUSIONS
CD-R discs are capable of excellent longevity, but achieving that potential requires diligence by both manufacturers and users. Manufacturers claims may be valid, or may be based upon flawed or non-existent data. Proper end-of-life indicators must be used to estimate longevity. This study has shown that BLER is not a universal indicator of media life, although most published longevity estimates have utilized BLER as the sole end-of-life indicator.
E22, E32, and BURST errors are valid end-of-life indicators. When present, they indicate a need for immediate duplication if a disc containing archival information is still readable. Such errors are not useful for estimating media life by extrapolating test results of discs that have been subjected to accelerated ageing. All quality indicators must be considered when selecting end-of-life indicators. This study suggests that total and peak E12 error rates as well as jitter may be useful indicators, provided that all other quality requirements are met.
High initial quality for each disc can only be achieved by managing variations in media and recording drive quality. Individual CD-R lot qualification should be employed where possible to confirm that manufacturing quality was high and was not degraded by subsequent packing, shipping, and storage events. Media handling and storage is very important. Both unrecorded and recorded disks should be archived in clean jewel cases in a stable storage environment of 10 C-15 C and 20%-50% RH, and protected from sunlight and other radiation sources.
CD-R media and drive manufacturers are responsible for product quality levels that support interchange and longevity. Not all manufacturers achieve this goal. Increasing demand may require new facilities or production lines that inevitably undergo growth pains. Technical advances can lead to new manufacturing processes that must be debugged. Price pressures may force compromises in quality that adversely affect baseline quality or increase fluctuations about that baseline. Identification of CD-R media and drives that support consistent, acceptable levels of interchange and longevity is the responsibility of the archivist. Proper vendor qualification and monitoring enables the user to confidently utilize the rich capabilities of CD-R, and rewards the manufacture with recognition of their diligent efforts to attain and maintain product quality.
Reliance upon brand names or upon readability of discs in one or a few drives cannot verify longevity. Confidence in longevity can only be achieved by initial testing of drives and media, through proper handling and storage, and by periodic resampling to confirm longevity or to identify a need for duplication while the original disc is still readable. Short cuts do not exist. The level of confidence will always be proportional to the amount of effort and expense incurred by the archivist in establishing and maintaining a high level of CD-R quality. Such methods are appropriate for all media types, and their proper application to CD-R information storage will satisfy the most critical requirements for interchange and longevity.