We have 2 year old laying hens and after this summer is over most of them will be culled out. We also have year olds and 4 weeks olds, so we add some each year and cull some each year, but about 2 years or a little over is all that we keep them.
Yep, when the hens turn 2 we buy (and now, hatch) their replacements, so when the replacements are ready to lay, the older hens are 2 and 1/2. Oh, and we usually sell them at a livestock auction. We get pretty good money from the auction.
Same here, anything over 18 months I start evaluating for their laying behavior and they start to rotate out. The longest I've kept anything is 2-1/2 years. There are plenty of people who buy them from us from Craigslist. I'm honest about the age and don't ask if they intend to eat them. Some people just want yard art and an egg or two every once in a while makes them smile!
Every February, I order a new batch of hens. When the new ones start laying well in July/August, I sell most of the older hens. Occasionally I have a favorite that stays, but in general I sell my hens when they are 18-20 months old and still laying well.
I don't like to carry 2 year old hens through the winter as they don't lay as well as the first year ones. Plus I don't like to wait until my hens are 2 and on the downward side of laying.
Plus I have a thing for chicks. Each spring I say that I am not going to buy any chicks, but either I cave at the feed store or my kids convince to get just one, which quickly turns into 10. So I end up having to whittle my numbers down every fall anyway. I don't mind carrying extra chickens in the summer months when they are cheap to feed, but I won't carry more than 20 through the winter.
This year I am supposed to be culling my nearly 3-year-old laying hens, but in reality I am only culling one out and keeping the rest as living yard art. The only one that didn't make the cut is my chronically broody bully. She's going to be coq au vin before spring is out because I am afraid she will kill my newbies. The rest have earned their place in our hearts and in our home for the remainder of their lives.
That being said, I cull my flocks as needed. Once a year the flocks are evaluated for fitness, and if I am not too attached to birds found lacking then they are culled. I usually cull out birds who have been problematic when they have made me angry for the last time.
It depends on what you expect from your flock as to the proper culling. Hens will lay best in their first 2 years, but as they age their production slows gradually. Hens can still produce 2-4 eggs per week at ripe, old ages of 3-6. These eggs are often LARGER than when they were at their most prolific laying stage. So don't think that older birds are not productive unless you desire peak production at all times.
I plan to start culling at three years. I'm in the process of building my flock right now, so that in two years, I will cull the oldest set of 3-4 hens, and bring in a new set of 3-4 pullets. My total flock size will be about 18-20 hens, with 15-18 laying hens at various laying ages. Cross your fingers for me! lol I've given this a LOT of thought.