Lifetime for human copyright, 20 years for corporate copyright. That’s the golden zone.
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Assuming you agree with the idea of inheritance, which is another topic, then it is unfair to deny inheritance of intellectual property. For example if your father has built a house, it will be yours when he dies, it won't become a public house. So why would a book your father wrote just before he died become public domain the moment he dies. It is unfair to those doing who are doing intellectual work, especially older people.
If you want short copyright, is would make more sense to make it 20 years, human or corporate, like patents.
Copyright is about control. If you know a song and you sing it to yourself, somebody overhears it and starts humming it, they have not deprived you of the ability to still know and sing that song. You can make economic arguments, of deprived profit and financial incentives, and that's fine; I'm not arguing against copyright here (I am not a fan of copyright, it's just not my point at the moment), I'm just saying that inheritance does not naturally apply to copyright, because data and ideas are not scarce, finite goods. They are goods that feasibly everybody in the world can inherit rapidly without lessening the amount that any individual person gets.
If real goods could be freely and easily copied the way data can, we might be having some very interesting debates about the logic and morality of inheriting your parents' house and depriving other people of having a copy.