I feel like it should be the life time of the creator of the work provided that person is still getting a significant percentage of the royalties. Otherwise something like 20 years.
That way companies might be less likely to force artists to sign away all rights to their work. So like "hey this kid could live another 50 years, so lets make sure he gets his percentage so we can keep control longer."
How would that work for anything produced by a company? If you're a continuing run of stories, and a random artist dies, copyright on parts of your product suddenly evaporate? Getting a job as an artist would be like making an insurance claim: with a risk assessment. Good luck getting work as you get older or sick.
Why would a copyright entering public domain cause a problem with your product? Public domain doesn't mean you can't use a work anymore, more the opposite really.
And they'd still get 20 years for a work made by a 90 year with a terminal illness.
Could companies not also say "hey, this kid could live another 50 years, let's kill them soon so their work will be in the public domain and we can profit from it"? Or would companies not want the work in the public domain?
I dunno what the patent duration is, but copyright should probably just be 50 years max IMO. If you can't make bank in that time without changing the idea up (and thus getting 50 years on the new version) you don't deserve it.
Originally I think it was closer to 20 years. Frankly I think 25 years is plenty. A quarter century is enough time to reward the creator of an IP and it respects the fact that all IP is built on top of the public domain so it's return is a natural part of the cycle.
In any case it's not like after it expires you could not trade on being the original. It's not like others could then come along and claim to have been the original creator. And if you kept making works those would each get their own period of copyright.
I agree with copyright in a sense that people should have a chance to profit from their ideas before it gets stolen, but you are right that it is way too long of a term. It stymies creativity when people can milk the same idea for many decades.
I would think for creative license like an idea for a cartoon or comic, 10-20 years is more than enough. Then they should try and make new characters or start competing with others trying to improve the character.