I'm looking for a collection of the most reputable sources on the lifetime of various types of media (hard drives, optical discs, magnetic tape, flash memory).
The ultimate question would be, what type of media is currently the best option for long-term storage?
Here is a good source for CDs and DVDs: http://www.cci-icc.gc.ca/publications/notes/19-1-eng.aspx (CCI Notes N19/1 Longevity of Recordable CDs and DVDs (2010) , Canadian Conservation Institute)re
Media lifetime is a red herring. All media types suffer from two key problems:
Write your data to some media and leave it on a shelf, and it will eventually become damaged and/or impossible to read. When this happens, you won't know. This is not a viable approach to long term digital preservation.
To ensure the longevity of your data you need to repeatedly check that it remains undamaged by verifying its integrity (this is easy to do by creating checksums for your data and then periodically recalculating your checksums in order to identify any data loss). If data loss is detected, repair is necessary with the aid of a backup copy (or two).
This means that the critical media characteristic is accessibility, not longevity.
For example, a manufacturer might claim that their specialist gold CD-ROMS are guaranteed to last 100 years. However, in order to confirm that their "guarantee" is in fact correct, you need to periodically verify the integrity of the data. Sitting in front of a disc drive, repeatedly inserting CDs so that you can do an integrity check every month is not a lot of fun if you have a lot of data.
High capacity and easily accessible storage media (albeit storage media with a limited lifetime) such as hard disk and magnetic tape remains the long term storage media of choice.
Keep the data accessible. Keep at least 3 copies. Keep checking the integrity of the data. Fix the data from a backup when necessary. Migrate to new media when it reaches end of life.