You're too kind, missing the drive to provide for the next generation is more than a minor nit. A tempting response is "So something like min(20years, authors

You're too kind, missing the drive to provide for the next generation is more than a minor nit. 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.