I know the posts in these threads are old, but I'm going to reply anyway
I think it depends on the number of chinchillas, how messy they are, and how large the cage is. On both of my cages (the large one has the female, the medium one has the 2 males), I change them (the bedding) every 3-4 days. The female's cage could go longer since she poops on the levels (they're solid, the males is wire and falls to the bottom) and if I vacuum, I could go a week without changing the bedding. I change both at once though to minimize the smell.
I used to hose down the cages when they were bad, but since I'm very close to being done with their brand new, furniture-style cage (2 sections, holds all 3 chins), I haven't done it in a while. The female's cage bottom is plastic and can easily be sprayed down and wiped clean. Sometimes I use a natural cleaner like Mrs. Myer's all purpose cleaner. Hose and some dish soap works with the wire. Once I get them in the new cage, I'll use the Mrs. Myers to clean the melamine levels.
FAQ 
How often should you clean out a chinchilla cage 
