Hero,
I filed concurrently, and my I-140 was not approved when I first did FP.
Add to that, that back in 2004, NSC unilaterally decided that they weren't going to even look at advancing I-485s until the I-140 was completed (their way of doing an end-run around concurrent filing, which the USCIS HATES).
So. while I don't know exactly when NC started, from luds and previous service requests, it coincided with the second set of FPs last spring.
So, was it may, or april, or 2004 who cares? Once NC last more than a month or two, you are basically in the black hole.
As to writ of mandamus, I'm considering. I think WOM has little chance of success.