Clean out of bedding?

[Corbeens]

Hi! I haven't been posting as much recently as I've gotten past all of my beginner questions and such, but I would love any opinions on this as possible. My dwarves are mostly on c&c bedding (with around 1/3 or more of the cage sand as they are robos) and they pee so little i've only seen physical evidence of it twice, once when it was in the sand and once when one was out in the playpen. Because of this, I was wondering how often I should clean the burrowing portion of the cage. The main problem is the poop, but that seems to settle out to the bottom of the cage anyways, so if I were to clean all of that out can I take out less of the bedding? I have no problem taking out the 2/3 a month but I was just wondering how efficient that is as it looks as fresh as new bedding even after that time.