The current issue of New Scientist has an article warning of our reliability on storing data on ever more fragile and vulnerable forms. There's an interesting side bar called 'How long will it last?' which lists the estimated longevity of electronic storage media. A note says 'actual longevity will vary greatly depending on storage conditions' so presumably these are average figures. Here goes then, in ascending order: CD-R (cyanine and azo dyes): 8 years CD-RW, DVD-RW, DVD+RW: 8 years Flash: 10 years Digital tape: 12 years Analogue tape: 20 years Audio CD, DVD movie: 25 years CD-R (phthalocyanine dye, silver metal layer): 25 years DVD-R, DVD+R: 25 years CD-R (phthalocyanine dye, gold metal layer): 100 years This is an interesting table. I'm surprised that regular DVD±R lasts longer than regular CD-R, for example. 20 years for analogue tape seems to me conservative. And also, it's kind of ironic that the best CD-Rs last about 4 times longer than commercial audio CDs. The article is an interesting read, and it makes you wonder how much of the billions of gigabytes of data being produced now will still be accessible in 20, 50 or 100 years hence, especially if there is a major catastrophe.