Peter Coggins asked about life expectancy of CDs.  I would field the
question to the Preservation Office of the Library of Congress if I were
still there.  Was going to suggest you phone, fax, or write them,
yourself, Peter.  But you seem to be down in the land of the kangaroo.

LC has done very extensive work on aging of paper.  They are now, out of
necessity, researching the new field of life of modern data-recording
media like oxide-coated materials, acetate film, phonograph records
(shellac, glass, plastic, or whatever), and optical disks.  I don't know
how much data have been developed, but that would be a good place to make
initial inquiries.

I'm sure a lot depends on storage conditions and environment, especially
temperature.  But I'm out of my depth when talking about data-storage
media other than paper, the traditional one.