My case:
My EB2 PD is: 5-5-2006
The I-485 of EB2 is already pre-approved.
We applied EB1b in Feb. 2010. I-140 was approved in 03/15/2010. The I-140 supposed to be linked to the I-485 for EB2. The interfiling has been more than 4 months. Our files are currently in NSC.
Good luck!