Yes, prevailing winds, in my limited 1.5 years experience, seem to be an important factor. Our typical wind is out of the south, and it is usually the skimmer sock on the north end of the pool that has enough debris to empty almost every day. However, the second most common wind direction we get is from the north and maybe northwest. We have a second skimmer near the south end of the pool but on the east side, as the south end of the pool is that useless sun shelf. When the wind is out of the north or northwest, that second skimmer gets most of the debris. So based on that, if we had open water at both ends of the pool, I'd be inclined to have a skimmer at the north and the south ends. Another thought, though. If you run a variable speed pump at a low speed, as we do, there is a point where there might be insufficient flow for two skimmers to work well at drawing in debris from the water surface. That's just a casual observation, though. At 1650 rpm, we have enough flow for our 12:15am to 10:45am pump running time to usually clear the water surface of leaves and debris with two skimmers, and regardless of wind direction, both skimmers collect debris. Someone else may have some science to support more or fewer skimmers.