Any mattress, including the Allswell Cool, can begin to sag over the years. However, Allswell’s warranty policy covers indentations greater than 1″-1.5″.
Normal body impressions are not the same as sagging. Over time, the mattress will conform to your body and form slight impressions. These are perfectly fine and shouldn’t cause discomfort as long as they don’t exceed 1.5″.
