Your cat's litter box should always be clean. This is because your cat’s health and hygiene is paramount. It is a common rule of thumb to change cat litter a minimum of once a week if there happens to be only a single cat, however, this can differ based on many aspects. One of them includes having multiple cats or if your cat has a habit of urinating often, the change of litter would be more frequent. The kind of litter also plays a role in the timing of changing. For example, clumping litters maximize moisture and odor retention so require changing less often. That and other ways of maintenance ensures that the house smells clean and encourages your cat to use the litter box without issues.