we tend to change out the pouch and wash it every few weeks. sometimes up to a month even. that might be a little long, BUT think about it, these critters live in a tree hollow in the wild. No one cleans their tree, unless they do.
We have two oversized pouches for the 7 glider colony, they pick one and MOST of the time all 7 are in the same one all the time, even if it gets a little stinky they usually don't switch to the unused clean one, until we take out the dirty one and wash it.
I would think one to two weeks for washing is fine.
I don't know what the brown is, we have neutered males and females, I sometimes find old food bites or a few poo bits in pouch, it's strong with their scent before washing.