Fill the litter box no more than halfway to the rim at a time, and change it about once a week. However, the exact amount depends on the type of litter box and the litter material. The litter thickness should be such that it doesn't stick to the bottom and the cat won't dig it out. Clean the litter box daily, approximately every one to ten days. If you notice the litter smells bad or becomes dusty, replace it completely with fresh litter. 
Consequences of not changing cat litter:
1. It will breed bacteria. If cat excrement is not cleaned in the litter box for a long time, a large number of bacteria will grow, and parasites may also appear, which is very unhygienic.
2. It can cause illness in cats. Cats that defecate in unsanitary litter boxes are more susceptible to bacterial and parasitic infections, leading to urinary tract diseases and other ailments.
3. It can cause cats to urinate indiscriminately. Cats are very clean animals; they can be quite fastidious and dislike defecating in a dirty litter box, so they will look for other suitable places to relieve themselves.
4. It can affect a cat's mood. If a cat doesn't have a clean place to relieve itself, or can't find a more suitable place, it will often hold its urine, which can cause the cat to become anxious and irritable.
5. It will affect the owner's life. If the litter box is not cleaned for a long time, the odor will be very strong, and the dry litter dust will float in the air, which will have a great impact on the owner's life.
