I too live in NJ and find that the wait time for longarmers is, well, long. From what I've learned, the pricing is about the same as other places. It certainly is frustrating that your longarmer is not better at scheduling. Even if, as the previous poster states, some quilts take much longer than others, it seems like she should consider that possibility (or likelihood) into her estimate for completion date. You'd rather be surprised with an early completion than a late one.
I'm assuming that when you speak to a longarmer and she says "one more week" (or whatever) that the quilt should already be on the frame or next in line to go on the frame. Your situation does make me wonder if she has a schedule of first-in-first-out or whether others move up on the priority list for some reason (equivalent to others cutting in line), which would make me very unhappy. Perhaps you could ask her to keep a list and show it to you when you drop off your quilt...so you know exactly how many quilts are ahead of you in line.
Meanwhile, I'd look elsewhere.