Im psycho obsessive about my litter boxes because if they start to smell Bf gets on his tirade about how the cats smell and he doesnt need that crap..(yes he is a grumpy old man at 28)...But I get the Special Kitty clumping kind and I get the biggest box I can and generally 2 at a time..And I need about 4 a month because Im always refilling the boxes and washing them out and all that annoying good stuff for them. Since I have to vacumn their room out every other day anyways I always try and keep their boxes super fresh and clean so Im not getting yelled at...