Digital data, if considered in some Platonic sense, doesn't degrade. However, the physical substrate required to store said data does absolutely degrade over time: hence the need to copy data to new media periodically. 'Tain't no way to get around the Second Law of Thermodynamics.
Not only the physical substrate, but the platform it runs on. Even 30 years (not much for a library/archivist) old software can bring substantial challenges. Much more so if it was a closed system like a game console, or DRM protected binary that may or may not work in an emulator (if said emulator exists).
I do wish that published software had a maximum license life, much like patents that would allow archiving.
