We’ve owned the Scoopfree for several years and love it. With one elderly cat, one tray would last about three weeks but since his passing we got two kittens. Theses growing girls required an additional box (total of 2) and burn through one tray each week, per box (total of 2 trays/wk). In between tray swaps, the units perform perfectly, with no mainatenace and easy cleaning. [This review was collected as part of a promotion.]