[SauronOfMordor]

The problem with long copyright periods is that works long out of print can be permanently lost if there’s no available copy once copyright expires.

14-28 years should be sufficient. 40 if and only if an electronic copy is given to the copyright office, to be archived until copyright expires, and then downloadable afterwards.

[zeugma]

The problem with long copyright periods is that works long out of print can be permanently lost if there’s no available copy once copyright expires.

Absolutely. This is one reason Project Gutenberg is such a Godsend. They are scanning in and making ebooks available for free download, and have been doing so for ages.

[zeugma]

40 if and only if an electronic copy is given to the copyright office, to be archived until copyright expires, and then downloadable afterwards.

I actually like the idea of the copyright office requiring that a digital copy be provided (Without encumbering DRM). The "EPUB" format is a fully documented specification that can be used with almost any document type, and is not "owned" by any particular company.

For any document type that cannot be documented via EPUB,(Perhaps an example would be musical scores) I'd recommend a DRM document type be developed and documented via the standard internet RFC methods that can handle it. That way you do not have to worry so much about bitrot associated with abandoned proprietary document formats.