Unfortunately, they are not that predictable in my neck of the woods. If they did not come back in 15 minutes, they probably are not coming back. They already found them a nice comfy little hole and probably will make that there new home. Would not surprise me if they are in Cameron Parish, LA by now. Ducks in my hunting area usually choose their resting, feeding, and roosting areas dictated by some environmental condition. Wind, ice, changing water levels. I might find 1000 ducks in a hole today, and if the wind changes directions tomorrow morning - I might not see one. Same with falling water or rising water. They might have been there today because the ice ran them out of another hole. They might be back in the other hole tonight with the thawing ice. More and more, where I hunt, scouting does not play the importance it used to. Now you have to plan tomorrow's hunt based upon the expected wind, water levels, temperature, and anticipated hunter pressure. It is awfully hard to move to another spot tomorrow when you had a good shoot this morning. But if you know there is a major change coming - you better plan ahead.