I don't know about the first part (and frankly I don't care) but my idea of the second part is the same length as a patent: 20 years. 20 years after publicatio

I don't know about the first part (and frankly I don't care) but my idea of the second part is the same length as a patent: 20 years. 20 years after publication all works irrevocably enter the public domain and are free for everyone to use for all purposes. 20 years after death unpublished works also enter the public domain or are ineligible for copyright. And the law that sets this would state that all existing works now have just 20 years copyright.