The repeat generally is confined to highly figured woods or those with knots. The most common # of prints is from 6-10, much of this is based on price, cheaper having fewer. I learned to sort them on my very first Pergo floor, it was a wide plank antique oak pattern with a repeat of 7. I was just popping open the boxes and putting the stuff down as randomly as possible when I noticed that 2 patterns were beginning to pile up. Time to fall back and regroup.
I was already out about 6 ft. from the wall, so I had a place to begin sorting. As we sorted, we also gave them names to speed things up, Big Knot, Long Knot, Crooked Knot, Clear, etc. This will (figure back in) it is also when we discovered that we had quite a few more of two prints and were a little short on another. Now it's time to get creative, you can use the ones that you have the most of for starting, finishing (they look a little different when cut) and burying under furniture. The trick is that you don't want too many in the same row and definitely NOT side by side, the center of the room is the most important. Art on the walls and furniture will lead the eye away from the perimeter flooring.
As for naming the planks, it really speeds things up when using help. You think ahead like a chess game and yell out, "Big knot, Clear, Crooked Knot!" and that's what gets delivered.