It seems to me that a reasonable compromise would be to make automatic copyright a relatively short term deal in the neighborhood of 15-25 years. But at the sa

It seems to me that a reasonable compromise would be to make automatic copyright a relatively short term deal in the neighborhood of 15-25 years. But at the same time, allow copyright holders to pay a fee to extend the copyright for a further term. If the fee went up on each term, it would encourage owners to only maintain their hold on particularly marketable properties, allowing the rest to lapse into public domain. As a side benefit, this would go a long way towards reducing the ambiguity that plagues older copyrighted works that don't have a clear owner, but still haven't reached a date where their copyright has expired. Either there would be a clear chain of documentation from when the rights were extended, or else you could safely assume the copyright had lapsed.