I was listening to the excellent Hello Internet podcast made by CGPGrey and Brady Haran, and in episode 3 they talked about copyright.

Copyright is about protecting investment, its about money.

So lets make it about money. I think copyright should be theoretically infinite. You should take the production budget of the work of art. Multiply this by some factor, and then if the art makes that much profit the copyright protection is removed. If a work of art isn't popular enough to make that much profit then it can stay under copyright protection indefinitely, until it does.

Yes, the obvious thing that will happen is that production companys will artificially infalte the production costs in order to maximise the profits they can make.

I still feel this is a better system than we currently have.