In one interview, Rick Rahn said they collected video from all over town and it took them a while to get to the one that had the good information on it. That was why he could not say exactly when it had come in nor how long they had it.
Thinking about this, I have wondered if -- once they found the helpful bit, could they then go to other video from others on the same roads and go back and forth up and down the street, piecing together the fact that CR was circling around and kept coming back to MT?
Would not each camera have a limited view? So, you see Mollie and a car on one; you maybe see the same car 2-3 times on that one camera, even after Mollie is long gone. So, he's circling around . . .
If you consider that LE has maybe dozens of videos from all over town, once they located something at Boundary and ??was it Middle??, then they hunt through the stacks of videos to find something a little farther up the road . . . . I think there's no way of knowing how much video they had and how much they had looked through before finding the gold nugget that started unraveling what had happened.