What's the objectively optimal copyright term?

This idea is far from perfect, this system is relatively impractical, it has more than a few flaws, and it still requires a shit ton of flushing out… basically:


Why can’t we just treat copyrights like public property currently in private holding, like a extended lease? In a ideal world I could see copyrighted media/material automatically starting a procedure (maybe through a special court system where a judge both represents the public/advocates for the material and makes the end decision, the current copyright holder would have to argue with evidence for being allowed to continue holding the said copyright in question) that would allow it to be transferred to Public Domain if it had not been used by the current copyright holder to further more artistic creation, advertising, appearances, showings, etc. for a period of say… 8 or 10 years? Just sending out takedown notices or acting as a copyright troll would not count towards use of the media (The obvious exemptions would be if it was still owned by a singular person who was part of its creation or its original creator or as part of a inheritance of either). It seems this might at least deal with the orphaned work or old classics that are still under copyright (personal relevance) but not being used in any means other than to send takedown notices.