The addition and replacement of cat litter should be determined based on the specific circumstances.
If the litter in the litter box is still usable, meaning it doesn't have a strong odor and there aren't large clumps on the surface, then you only need to clean the litter box regularly and add new litter as needed to maintain cleanliness. In this case, it's not necessary to completely replace all the litter.
However, if the cat litter has a strong odor or large clumps appear on the surface, it needs to be replaced completely. Cat litter usually needs to be replaced every 2 to 4 weeks, and some types even need to be changed monthly. This is because failing to clean the litter box and change the litter regularly can easily lead to bacterial growth and cause urinary tract infections in cats.
