[cypher]

Simple answer, never!
I just spot clean where they pee as needed & then do partial cage cleans every few weeks or so, I find they tend to get a lot of old poo left around the wheel area so I'll do that & if they've been doing a lot of digging (mine are all Chineseys so they do!) & get old food etc mixed deep into the substrate I'll do that when it looks like it needs doing but I never do the whole cage at once, it really doesn't need to be done & it's better for the hams to always leave some of their scent in the cage.