3-5 years AT MOST. 20 years is an eternity in today's world. Most of the revenue a creative work generates comes in the first few months after its release anywa

3-5 years AT MOST. 20 years is an eternity in today's world. Most of the revenue a creative work generates comes in the first few months after its release anyway. For movies, the revenue from outside of cinema screenings is not even considered for statistical purposes. It would also make some sense to make copyright non-transferable.