Like many people, I back up my raw files to CD for archiving. Typically, I'll make two copies of everything; one copy goes into a small fire-proof box and the other into a drawer for when it's needed. I've known about the possible instability of CDs and the danger of losing data for a while, and it's been an item on my "one-of-those-things-to-do-sometime" list for a while. The 3 Nov '03 edition of The Langa List was in my mailbox this morning, and the first item was on this topic. Fred was following up on a story that appeared in the Dutch magazine PC-Active, which suggested that CDs could become unusable in less than two years. (if you can read Dutch, here's a link to the article, if not here's a translation courtesy of CD Freaks.) Well, I bought my first digicam - a Digital Ixus - in Dec '99 and my first DSLR - a D30 - in March '01, so I figured I'd best take a look at things.
Update 5 Feb '04: The US National Institute for Standards and Technology has published a report, Care and Handling of CDs and DVDs, which gives some additional guidelines that I've added to my original list. The additions are mainly with respect to handling, in particular, storing them upright, like books.
First some guidelines on the use and handling of CDs:
Do handle the disc by the outer edge or centre hole
Do use a felt-tip pen intended for use with CDs, otherwise use a non-solvent-based felt-tip pen on the clear plastic centre. Otherwise you may scratch the disc or the ink may react badly with the disc.
Do put CDs in sleeves or on the spindle that often comes with them, and store them in a cool, dark and dry space and store them upright, book-fashion.
Do wipe from the hub to the edge, not in a circular direction, if you must clean a CD - scratches across the have less effect than those that go around.
Do use CD/DVD cleaning detergent, isopropyl alcohol or methanol to clean stubborn marks.
Do make duplicate copies.