I think 7 years, or 14 if renewed would be better. The early copyright systems came into being in the 1700s; present-day distribution chains are much faster.

I'm not sure the speed of distribution is the relevant consideration. I can distribute a book I publish much more easily now, but the book isn't written and edited any faster.

But it can become known/popular much faster, I would assume.

That would be my assumption, too, although it'd be interesting to try to find data to confirm that. Books (picking the field I know the most about) could still sell really well and really quickly back in the "old days"; reviews often came out in advance of the book, bookstores could take pre-orders, and so on. I don't have any real data about how the "old way" balances out against the "new way."

That's true. But the audiences are surely much bigger now. (Both gross population and literacy would have been lower.)