I noticed that although most couples get approvals at the same time, there have been quite a number of cases in which primary applicant got approval first, and spouse has to wait for 1-3 months. I got approval on 12/3/04 (ND 10/2002) and my wife's is still waiting. Here is my theory why this happens: my visa history is relatively simple (F1 -> H1 -> GC), while my wife's is more complex (F2 -> F1 -> F2 -> H4...). If anybody has the same situation please share.