I cycle birds in-and-out of my flock each year. I replace at least 1/2, if not more, of my hens with new pullets. I keep no birds longer than their end of the 2nd laying cycle which is about 30 months of age. By doing this, I have a steady supply of eggs year round, take advantage of the 1st 2 laying cycles of any bird's life, and have birds that still have enough production left in them to be of value and pose no issue in finding people who want to purchase them when I want to cycle them out of my own flock.