One problem with requiring people to renew their copyright is that a lot of people will simply forget. There are people who produce hundreds of little pieces every year, each of which generates little revenue on its own. Should they renew their copyright on each and every work at the end of every year? Currently, their works are automatically copyrighted, even if they don't put up a copyright notice.
I think you should wait X years (where X is around 10-20) before that formula kicks in.
I think you should wait X years (where X is around 10-20) before that formula kicks in.