I must add, that as a writer of historical fiction, I don't know where people get the silly notion from, that in order to write about a place, you have to visit it.
Writing plays did not take that long, all you really need is a story, which you can cobble together from many sources, a bit of dialogue, a dramatic flair, and hey presto. If an improvisation goes well, you incorporate it.
Shakespeare, to me, at any rate, always felt as if written by an actor.
Elizabethan/Jacobean theatre would have been like cinema in the 1930s.
Selling his books wouldn't have taken that long either!!
Another possibility is that Shakespeare borrowed books from his friends and acquaintances.
The Davies I reffered to, is Sir John Davies, a poet much neglected by scholars.