Within the first couple months, we noticed that both my wife and I were forming lower areas on each side of the mattress, with a hill in between us. We are both about 160 pounds. The store manager suggested we rotate the mattress, and we do, but there is no position that removes the hill between us. Because the King mattress requires a set of box springs, I can't help thinking the hill is caused by the edges of these two together down the center. The photo doesn't quite capture it, but there is a visible shadow on either side of the higher center.