Music, I think, has the shortest shelf life of all copyrighted material except software, but I'll get to that next. Movie soundtracks last maybe a little longer than that if the movie was very popular. In the cases where an artist had one or two hits and then kind of vanished, the album will probably disappear shortly as well. Generally, only the hits are available after any length of time, Greatest Hits collections or Top Ten for the year collections. Album cuts are forgotten, stuck away in the Record company's archives, never to re-emerge.
Software is different from most other copyrighted material in several important ways.
Leaving off the idea that software is only licensed and not purchased, software also consists not only of the executable program, but also source code, both of which are covered by the copyright. Because of the rapid changes in the computer industry, software should lose its copyright even more quickly than other copyrighted works. More importantly than a new release, only software currently being supported by the creator should be covered by copyright. Ending support for the program should be considered abandonment. Also, software that won't run on current technology should either be updated so that it will, or abandoned to the public domain.