I have 36 rabbits inside my house (rescue). I only have to change my
litter once a week. I use wood shavings (pine) that is sold as "horse
bedding"...$5 for 9+ cubic feet. Each litter pan has about 2 to 3 inches
of this, depending upon the size of the rabbit, and I then sprinkle Woody
Pet on top of it. Usually, I don't smell the boxes until the 6th day...just when
the boxes are due to be changed. Each of my cages have litter boxes.
This is more efficient than using the pull-out drop-pan as you can't put
that much litter into them...so, they smell.