Here's something similar that we use at our house. I have 2 litter boxes for 4 cats. I used to keep 3 for 3 and no one would use the 3rd box. So far 2 for 4 is working.
I guess you'd call me complusive scooper, stuff doesnt stay in the boxes long before I scoop. Probably scoop 3 x 4 times daily. Overnight (while I'm sleeping) is longest it stays in the box.
I like a clean box they like a clean box. I wouldnt want to potty in a dirty stinky box either.

WalMart and PetSmart carry them in all sizes.

Here's the link to the site of PetMate. Sizes etc.
litter box