In keeping in line with the other VBBs on the site, I am bringing a policy for books that are owed from previous rounds. I believe that 6 months months is enough time to read & send a book.
So, what that means is, at the start of Round Four (March) anyone who has books owing from Round One (September) will be unable to remove books from the VBB until their books are sent.
I really don't think it is going to be a problem as just about all the books from Round One are sent already, but it is good to have an official policy :)