Right, it is a limited right because it builds an artificial monopoly. Copyrights were intended to have a similar life cycle to the patent. It lasts for a few years, possibly with a single extension if you can prove certain things about how you are using it (that you are actually using it, not just squatting on it to prevent other people from working with it).
It is a bit broken that the term limits are so different today.
> a clear and simple expiration
> life of the author
> (at least in the US
I think you included several reasons it is not clear and simple. Life of the author is real hard to define and gets shifted by "work for hire" rules, especially because so many things subject to copyright beyond books don't/cannot have a single author.
On top of that, different countries have different definitions. The Berne Convention muddies the waters that "the strictest country's definition wins" but also provides carve outs for "when in my own country I only need to worry about my own country's rules" some of the time.
Different countries have different orphaned works laws, though the majority do not today believe copyright expires on orphaned works it just gets "lost" who owns the copyright. Most countries have "copyright is automatic" laws (and the Berne Convention supports that) and "copyright is assumed and must be disproven" laws (which again the Berne Convention supports). All three of these things make the question of "is this under copyright and by who?" far from clear. (As the article here goes at great length to provide just one example of such confusion and opaque expiration information.)
The world's copyright systems lost "clear and simple expiration" decades ago.
