Well, I think that those in favor of life + forever on copyright should also be in favor of a yearly charge to maintain that copyright. It works for land.
And I think this amount should fluctuate based on the financial needs of the city/state/federal government in which the copyright holder lives. It works for land.
In addition, if the copyright holder cannot or will not pay the absurdly large amounts of required taxes...the government should be able to take away that right and sell it to the highest bidder. It works for land.
Of course, there are a lot of people who won't ever be able to afford copyright...some will save up for it for their entire lives. And still not make it. It works for land.
Plus, there should be a hard limit on how much copyright is available to be sold at any time. Hey! They aren't just making more copyright, you know. Cause that's the way land works.
Oooh! I should be able to put a lien on your copyright if you owe me money. That works for land, too! Plus insurance. Gotta have insurance.