Well, I will tell you what we did, that USCIS will not tell you. My husband got his FP appointment notice one week before his appointment date of June 4 in Atlanta. I received my FP on June 3, to appear in Charlotte, NC on June 10th (today!). This is ridiculous as I am about 350 miles away from Charlotte, Atlanta is much closer. So when my husband went in to the Atlanta ASC, he asked why I had to go to Charlotte and they told him, "is she in the car, if so, bring her in and we will do her biometrics right now". I did not go with him on June 4, but they told him I could come in on Saturday, at 1:00 p.m. as a "walk in". So I did, and had it done, but I had to send a letter by certified mail to USCIS in Charlotte advising them I would not be at the appointment on June 10, as I had them completed by the Atlanta ASC. You can go to any ASC as long as you have the appointment notice in your hand.
I generated a SR (by calling the regular Customer Service #800-375-5283) on 5/14 and then an FP appointment was sent to me dated 5/22/08...so I don't really know if it was a fluke or coincidence or it got the fire burning again on our files...who knows, remember it is the federal government we are talking about...
I would call and generate an SR.