For best results, replace the litter tray every 20 - 30 days for one cat, every 10 - 15 days for 2 cats, or every 7 - 10 days for 3 cats. You might need to replace the litter tray more often if you have senior cats, kittens, or cats who eat a diet high in crude fiber, ash, and by products. ScoopFree™ litter trays can be used by themselves as portable, disposable litter boxes. Scoop the waste under the waste compartment or replace the tray when needed. Mix the litter daily to reduce odours. Most cats adapt quickly to using the ScoopFree™ litter box.