>But, devil’s advocate, I haven’t heard a super convincing argument as to why something I make should ever revert to public domain, especially while I’m alive.
Because you've got it backwards, you have no inherent right to any intellectual property you create, it's a legal fiction. Before copyright was a thing, freely copying and remixing the ideas and stories of others was the default. Once an idea is out there, you have no moral right to tell others they cannot share it.
Copyright is an attempt to give an incentive to people to come up with more good ideas and stories and music, but the default is that they belong to everyone.
Because you've got it backwards, you have no inherent right to any intellectual property you create, it's a legal fiction. Before copyright was a thing, freely copying and remixing the ideas and stories of others was the default. Once an idea is out there, you have no moral right to tell others they cannot share it.
Copyright is an attempt to give an incentive to people to come up with more good ideas and stories and music, but the default is that they belong to everyone.