Yes, my postings in the mailed monthly statements do lag, also. My latest statement's at home, so I can't say by just how much, but I don't think what you have is unusually behind.

Northwest usually posts the miles from a flight within 2-4 days on their web site. BUT you can't use it to see what flight or flights the miles were from since they only list mileage totals, not each actual segment like Delta does. If Northwest ever goes to this, you won't have to worry about the mailings.