As a counter-example, there were some great sci fi novels written in the 80s and 90s which I'm only just discovering & I fully believe the author still deserves

As a counter-example, there were some great sci fi novels written in the 80s and 90s which I'm only just discovering & I fully believe the author still deserves money for them. How about 14 years from the date at which the author transfers the copyright to another party, or lifetime of the author if they don't transfer it? That said, I totally agree that authors lifetime + 70 years is too long. Take off the extra 70 years & I think you've got a fairer figure.