Minecraft wiki entry for Egg_farming, associated text: This despawn timer and inverter will enable the clock for 5 minutes only, letting you hatch 500 eggs at a time (about 31 stacks, producing an average of 64 chickens). There is a bit of a trick here: Since the clock has a period of 0.6 seconds, 300 seconds gets you 500 cycles, but the clock and dispenser are faster than the hoppers feeding the dispenser. The hoppers alone could deliver less than 375 eggs to the dispenser, but the eggs in the bottom dropper give just enough of a head start to cover a batch of 500. As noted above, the chickens will need a bit over a real-time hour to replenish the eggs used; if you don't want to wait for that, you can harvest the chickens as soon as they're mature, then run the egger again and let the second batch refill the chests while you do other things.