Then just make it the rule that the copyright expires after 30 years or when the author dies, whichever comes last.
I am fine that estate gets to keep rights for whatever period is left. If estate is dissolved ofc rights would also end. So they can't be orphaned. Either someone has them or they are public domain.
Why not just 30 years? Patents get a flat 20.
Not that I'm arguing for 30 per se, just that I don't see what goals of copyright would be advanced more by adding an "or until death" complication.