It is best to contact your supplier early. I have already ordered packages from my supplier two weeks ago, for pickup on the first week of April. You could probably wait until Jan. or so, but most don't charge you until you pick them up anyways, so I wouldn't take a chance. If you could find a supplier locally that you could pick them up that would be best, many times they show up with alot of dead bees. Also, I would recommend starting with at least two packages, if its your first bees. You may find it to be beneficial to the survival of the colony, I did.
Hope all goes well, Daniel