When Mickey Mouse was created (1928), copyright was 28 years that could be reupped once for an additional 28 years. So according to those terms, Mickey Mouse would have ascended to the public domain in 1984.

IMO any change to copyright law should not be applied retroactively. Make copyright law to be what is best for society and creators as a whole, not for lobbyists representing already copyrighted material.

> IMO any change to copyright law should not be applied retroactively.

Careful, if we were to shorten copyright, not doing so retroactively would give an economic advantage to franchises already published over those that would get published later. As if the current big studios needed any further advantages over newcomers.