Well, I know the codes that are published in Sunday travel sections can usually be obtained by Saturday-- because travel sections go to press early. I subscribe to the NY Times, and they deliver a few of the Sunday sections with the Saturday paper, so I can see the new codes a day early (or I can see them on Mousesavers! Since Mary always updates right away.) I think it is correct that you usually can't start booking until Sunday, but at least you can find out about them early and be ready.