My case was approved this week. Below please find the case info for those who want to know.
EB2, NSC
Priority date: 3/16/05
I-485 date: 5/27/07
Approval date: this week
My wife and I filed separate cases. It did not seem to cause any delay for this duplicated case filings.
I called USCIS this week and told them that my application is more than 30 days outside the processing time and put in an inquiry. Very next day, the case was approved. Maybe it's just a coincidence.
I think contacting your district congressman/senator will only help but not that much. My takeaway is you should contact them if you have not done so.
Good luck to those who are still awaiting.