Three boxes for two cats (because the boy is so darn picky!) - Cat Attract litter (again, the boy!) - scoop twice a day (sometimes more if I'm home and one has been used) - and completely empty, wash out, and replace litter once a month. I usually buy new boxes once a year, because I think the plastic does end up retaining the odor by then. I used to use the liners, but even with declawed cats (they came that way), they ended up ripped.
But, it does get down to whatever makes you, and the kitties, comfortable.
But, it does get down to whatever makes you, and the kitties, comfortable.