You may read us, and other stores selling comic books, referring to something called Final Order Cutoff. In the comic book industry, there are initial orders and then Final Order Cutoff. Initial orders are the preliminary orders stores put in with Diamond Comics, the primary comic distributor. If you order any toys, magazines, manga or anything pretty much not a comic from the primary comic publishers (Marvel, DC, Image, Dynamite, Vault, etc.) we need to know by the date of initial order submission, which is generally the last Thursday of the month. Diamond then puts in orders on all of the non-comic items based on the orders we submit and will sometimes, but not always, order extra of an item. For example, magazines are usually ordered based on the numbers submitted at the initial order.
Final Order Cutoff takes place about 3 weeks before comics and graphic novels from the major publishers arrive in the store. This is the last date we can guarantee to get books from them. After these orders are submitted, print runs for the books are set. The publishers may print extra copies, although Marvel generally does not. If they do, we can order books after the FOC date but in many cases, those orders will be canceled.
So in short, for anything except comics from the major publishers, we need your orders in by the due date for the Previews catalog, two months, at least, before expected release. For comics and graphic novels from the "major" publishers, we need your orders in at least 3 weeks before release date to guarantee the books for you.