Professional time here--

Preservation is a large part of what we do. Average book life is about 30 years, but that is ver dependent on acids and stuff in the paper. Conditions wherre the books are kept also play a HUGE part. Humidity, insects, and damge play a part too.

Currently, microfilm is the most stable way to preserve stuff. BUT try getting someone to repair a microfilm reader...and believe me I WANT ONE FIXED. Magnetic tape is bad cause the chaged areas lie on top of each other. 3-5 years or so with them. Not sure about CD's, dvds, etc, i am thinkng the problem with that is the players for the media. That could be the limiting factor with them.
NASA has tons of magnetic records of the data from testflights, etc, but nothing to read the tape with...

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"I'm done with propagandists who are willing to use any issue - race, cost, deterrence - to spare murderers' lives. Their attempts to shame a country out of delivering justice are terrorism of the intellectual variety." Brian Hickey

"The right to bear arms is the right to be free."
A. E. Van Gogt
THe Weaponshop of Ishtar