I completely clean every week. Sometimes a day or two longer depending on my schedule. They're in 18" x 24" bottoms so they get dirty in that time frame. Once I can even remotely start smelling them its time to change. What with their poos and their hay and those that like to dump their food, i change it once a week no matter what. Plus my chins LOVE clean cages, sometimes there are slightly bigger chunks of pine for them to chew on, which they love. We get bedding cheap so maybe its not so big of a deal, but i never feel like i'm "wasting" good bedding.