I really do love my Genie. The box says the granules last 4-6 months. However, I'm adding about half a box a month (with 2 large cats). This is in addition to other reviewers suggestions that they sweep up the granules from the floor, wash, and put back in the box. I do sweep a large amount from the floor as well. As other reviewers also noted, a large amount does get flushed for sticking to the waste.
I have a cat mat, but the granules still get tracked all over the house! I've upgraded to a much, much larger mat. So, I'll see how that goes.
Also, I hope the large amount of missing granules is simply due to the cats getting used to the new box (installed in December).
Yes, all cats are different and a box every 2 months is a bit too fast for 2 cats. So, see how your mat is doing and we will give you a call to insure your unit is functioning properly.