Indeed they do. The river image is an excellent one for time, - As a white water rafter I view a river as cfs, cubic feet per second. Each river is different. For time, its speed of passage is different for different ages. A four or five year old has little in his memory bank, and each day seems very long. By mid-life days are obviously much shorter, and even faster for octogenarians. So memory really does matter. The UI has a memory of at least 13.7 billion years, but we have no idea of beforehand, that is, behind the Big Bang.