Space is a big factor, but also the deep litter method is AMAZING if you keep food and water OUT of the coop. My ducks have been outside in their pen and coop for 4 1/2 weeks (they are 8 1/2 weeks old) and I have yet to clean my coop. I have 6 ducks in 24sq ft (I may get 2 more ducks and keep this same coop size in a couple of weeks). I go in the coop once a week and mix mix all the bedding up and have had zero issues with smell or a lot of poop in the coop. I started my deep litter method right when I put them outside with one 20lb bag of bedding pellets (people use these in horse stalls a lot), a decent layer of pine shavings, a THIN layer of DE, and a decent layer of straw and 4 1/2 weeks later I have not had to add any layers or clean the coop. The deep litter method is made to only clean the coop once or twice a year, so I'm crossing my fingers!