[jack9]

> Is that irrelevant because the developed asset is intellectual rather than tangible?

Copyright has a sort of enthalpy (an appreciation) that grows into new forms of protections with socio-techno changes increasing the value, as opposed to a depreciation. The value is also appreciated by how much it's already been used to make! (e.g. Star Wars) Without physical entropy, like a building, you have a very different economic mechanism. The benefit to the originator's estate is not the single determining factor. Copyright is bad, in the current form. A simple depreciation factor would be far superior to the copyright expiry.