I keep mine at least 12 inches deep, building up to the deepest measure one layer at a time. Using a pitch fork turn it over, mix it up and let it dry out in the summer heat (put the girls out in the run for a few hours and don't let them back in to poop on it yet). Sprinkle with a good dose of food grade DE. As long as you keep it deep, dry, clean, turned, sprinkled with DE you might be able to make it through most of the year without having to rake everything out and start over.
When you do get to the point where you feel like (or it smells like) you need to clean it all out make sure you put it in your compost pile and let it breakdown over time. Next spring you will have amazing soil material to add to your garden, plant beds or flower pots.
Good luck.