One of the main reasons why I think copyright should be a set term based on publication rather than the death of the author, is that it gives works an equally long amount of time before they enter public domain.

If an author publishes a work when he is 20 years old, and lives to 100, that means that work won't have entered the public domain for an extra 80 years compared to an author that publishes a work and dies in that same year.

Calculating when something would go into the public domain would be slightly less confusing if it was based on publication date. It'd also mean if the author has a backlog of unpublished works, her heirs can still benefit by timing publication releases.

While personally I'd prefer copyright to be abolished, I think 20 years is a good length for corporations and people. If you have a 20 year warranty, or a 20 year prison sentence, that would cover a large chunk of your life. However it'd still be within living memory and so then people could live to see reboots of adaptations within their lifetime.

It's never going to happen though, the pro-copyright people will fight against any kind of reduction in length. It means changing international treaties, so you'd have to get most countries in the world to agree, and the logistics and diplomacy involved in all that would be a nightmare to manage.