Just that it doesn't get gross and tamped down and wet. The chickens pretty much stir it up themselves, though, with natural scratching action. (Sounds like a commercial: Now, with Natural Scratching Action!)
Did you know that chickens raised on deep litter will get 100% of their protein needs from the bedding? I don't even want to wonder how, but that's what I keep reading about the DLM.
this is a great question since I didnt know about "stirring" the litter till about 2 months into it. Now I do it every other day, and DE it once a week, and pine shavings it every other week. Been doing it since day one and it works great!!! the stirring makes it so fluffy again and takes the smell if any right away!
I throw a little scratch in my litter once in awhile and my birds do a lovely job of miximg it up. It also helps keep the poop in it dried out. I also sprinkle FOOD GRADE DE in it.
Stirring helps keep it dry. I also like to throw scratch on it in winter and the chickens stir it for you. They also love to dust in it..sounds gross, but no bugs. As long as there is no moisture or smell, you're doing it right.
I have sand now but I think I'm going to switch to the deep litter when I build the new coop next year. It just seems so much easier and better overall.