One minor nitpick: "Reducing the duration from "Year of Authors death + 70 years" down to, just "Authors death", for example, clearly couldn't lead to any given author producing fewer books."
You can't know that. Lots of make money specifically to leave to children, and for many others it plays a significant role.
I agree about all the other points - there is a lot of unknown in this field. I'm just not crazy about people saying "let's scrap this at least partially working system, and replace it with something I just made up". I'm especially not crazy if they don't even demonstrate a basic understanding of the issues.
He was slightly more swayed by the moral argument: his children had done no work for this income, so why should they be preferred over the rest of society in benefiting from his creative output?
A tempting response is "So something like min(20years, authors remaining lifespan)" but that could leave early work (often less commercially successful) with an expectation of a longer copyright duration than later work.
A fixed period risks letting copyright lapse in an authors lifetime, which is certainly offputting to anyone who, for example, dislikes fan-fiction. So we move towards "authors remaining lifespan + rough average lifespan" as a compromise.
Seems reasonable, although I find one way to increase my understanding of any issue is exactly this kind of discussion.
Authors have managed to produce novels while holding down demanding full time jobs (or in at least one bestsellers case, still in full time education) at the same time. It is not necessarily the case that the only way books get made is full time writing.
You could also argue that the reduction in books from reduced copyright would be balanced by an increase in currently unwriteable "remixes" of existing works. Copyright could be, for example, the only thing holding back an explosion of people making enough to live on publishing fan-fiction. Who speaks for them?
There's still scope for a sweeping reduction, in the States at least. Reducing the duration from "Year of Authors death + 70 years" down to, just "Authors death", for example, clearly couldn't lead to any given author producing fewer books.
I absolutely agree that if there is a forum on the scope and duration of IP, small-money authors should be represented. It doesn't seem like that will be happening any time soon though.