I think it should be for a lifetime of the original author and non-transferable. The system is already rigged very much against artists, it's amazing how many people still contribute to culture under the given conditions. I don't see any reason why someone who writes a Christmas song or a novel shouldn't have a possibility to get payments for their works until they die, for example. However, I have a lot of problems with the bizarre extensions that companies and heirs have gotten for work they haven't created on their own.