Even the Economist recommends maximum 14 year copyrights... but then goes on to blow it:

However, to provide any incentive at all, more limited copyrights would have to be enforceable, and in the digital age this would mean giving content industries much of the legal backing which they are seeking for copy-protection technologies. Many cyber activists would loathe this idea. But if copyright is to continue to work at all, it is necessary.

Economist.com | Copyrights