How long is the lifetime of DVDs, and what options are there to back up documentaries and films? Chris Szejnmann
Commercial DVDs are expected to last more than 50 years, assuming they are pressed correctly on good quality media, and then stored in a cool, dark, dry place. Heat, humidity, handling and atmospheric pollution are all believed to reduce the life of optical discs, based on accelerated ageing tests, but nobody really knows.
DVDs that are burned separately, perhaps as backups, could last anything from 20 years to 200 years. However, read-write (RW) discs should never be used for archiving: they are not as stable and many may not last 15 years. According to a study by America's National Institute of Standards (NIST) and the Library of Congress, some could last only two years. There's a summary at The X-Lab: Optical media longevity.
Optical media are very variable, but Digital FAQ has published a brand media guide. Discs made by Taiyo Yuden in Japan are generally reckoned to be about the best, along with Hitachi Maxell, Sony and TDK. Some firms offer DVD blanks designed for archival storage. For example, Delkin Devices sells a 300-year Archival Gold disc and MAM-A has a Gold Archive DVD-R.
Obviously, you should still store your archival DVDs vertically in jewel cases or special boxes in a cool, dry place. You should also avoid writing on them, sticking anything on them, or touching their surfaces. MAM-A has a PDF of handling instructions. Even then, someone maintaining a serious archive would want to check sample discs every five years or so, and consider re-copying discs to fresh media. Under the circumstances, the cheapest and best backup of a commercial DVD is probably another commercial copy, stored archivally.
Either way, bear in mind that DVD is a heavily compressed, low-resolution, error-prone format, and there might be 80GB or more original data squidged down to less than 5GB. A DVD movie is not equivalent to a master tape. It's just a cheap format that works well for replaying movies on domestic TV sets.
