This topics emphasizes that if long term retrieval is a required then this has to be designed in from day one.

I have worked on a project to retrieve data from 7 years worth of backup tapes and it was painful. The backups were designed to protect day-to-day OLTP and not a data warehouse type operation.

Music lost from the 80's and 90's? Playing devil's advocate is that necessarily a bad thing?!?!? If it was any good then it is probably still being played on independent (UK) radio and definitely is by my noisy neighbours!

As to the long term worth.....if you've ever cleaned out your house and brutally got rid of all the things that "might have been useful one day" but somehow never were its amazing how much you don't miss it, or in many cases even remember you had it.