The problem with copyright is that it is used as an excuse to deliver the good idea to protect the new authors who are still alive, in the same package with the bad idea to let unspecified number of loosely related and unrelated people feed off free money source created by long dead authors decades ago.
I think part of the idea is that whether the creators are dead or not, having copyright and "unrelated people feed off", still maintains an economy over the item and gives it monetary value. Whereas if it was de-copyrighted it would lose that value -- everybody could just copy it.
E.g. Disney only being able to create or allow the creation of Mickey Mouse stuff (t-shirts etc), leads to a large business for them, taxes for US etc. (Plus pays a lobby to ensure longer copyright). If Mickey Mouse was suddenly public domain, that would stop and its characters would be devalued very fast, with everybody competing with ever cheaper products with him on.
Twenty years ought to be enough to recoup your investment, but I'm open to compromise. In any case, (rougly) 150 years, as it currently is, is way, way, way, way, way, way way too long.
Isn't letting them keep their copyright for long, an even stronger inventive for OTHERS to come up with some new characters? (in order to compete with them).
Ever notice how restaurants and movies never use "the Happy Birthday song"? That's because Warner Bros claimed copyright on it for decades. Another part of our culture that can't be used thanks to copyright.
There are plenty of films, plays, and TV series based on works in the public domain. Romeo and Juliet, Pride and Prejudice, and Sherlock Holmes to name just a few that come to mind. Should those creators be required to pay tribute to the descendants of the long-dead authors in order to use those parts of our shared culture?
Being granted exclusive protections during your lifetime or for a reasonable period of time after the creation of a work is defensible. De facto perpetual protections afforded to the artist's grandchildren (or great^n-grandchildren), not so much.
Could Disney have become this successful without free access to public domain works like Cinderella, Snow White, Robin Hood, The Jungle Book, One Thousand and One Nights, The Sorcerer's Apprentice and so on and so forth? Possibly. But insisting that their works should be protected far beyond the protections their source material ever had is hypocrisy at best, anti-competitive at worst.
No, it wasn't.
The first copyright law adopted under the Constitution may have established that length, but that's a very different thing.
I think you have the whole process upside down. Digital media already has no value, and it can already be copied freely.
The changes in the law that Disney and other copyright maximalists are doing is attempting to re-value digital media. So, the only option open to them is to push for ever more draconian laws simply to protect their broken and outdated business models.