Usually, people wait two years to sue them. However, now you can do some primary work for your lawsuit. For example, contact senator, first laday, congressman... Through these ways, you will get some evidence that shows that your have no other means to let FBI and USCIS to work on your case.
details you can find at
http://niwandwom.com/
ALthough some districts are hard to win the case, the lawsuit will give FBI pressure to work on your case.
If you lose the case, it will not hurt you at all.
Good luck