Cornflake the chicken was not harmed in the shooting of this photograph.
A chicken has a potential lifespan of 10+ years when given proper care, and that should be considered before you add a laying flock to your home, as should what you plan to do with them when they stop laying. It's hard to justify keeping an animal around that only consumes on a homestead where everything must earn it keep. After 2-3 years of laying, a hen is past her prime in egg production. In most cases she will be processed in a canning jar; even though we'd all love to provide a rent-free home for the remainder of their lives, it isn't always in the cards or the budget to do so. But there are some jobs that a veteran flock member can do — even if she isn't producing eggs — that makes keeping her around worthwhile.
Like adolescents in every other species on the planet (humans included), young flock members can be a total pain in the rear end. They sleep in nest boxes and cause poopy eggs; they fight over food and manage to sit inside the feeders to eat and then get stuck; they find new and exciting ways to get out of the run; basically they have no idea how things work in the coop. Having older flock members present who know the routine can help the teenagers figure out when to return to the coop at night, and that they sleep on roosts not in nest boxes. The teachers show them where to take dust baths, where to scratch and peck, and how to eat at the feeder like a decent member of the flock. Flock matriarchs can kick a little butt, too, to teach newbies their place in the world and knock out some of their cockiness. Before long, they will behave and follow the routine just like everyone else in the coop.
There comes a time when flock expansion is needed, and sometimes heat lamps and brooders aren't ideal. Sometimes certain hens are really bad moms and don't sit on their eggs for the full 21 days. Sometimes hens are homicidal and they kill all their babies as soon as they hatch. Enter the broody hen surrogate mom. They go broody at the mere sight of two eggs nestled in a nesting box and try to hatch them, and they happily adopt any abandoned chicks. Being a momma is their calling, and that's why broodies will always have a home in my flock whether or not they lay eggs.
Broodiness however, can at times be unwanted or become dangerous to the hen if her need to be a mother isn't satisfied. Check out this article from the Chicken Chick that tells you how to safely break a hen of broodiness if the situation calls for it. I love her method, and I have used it many times to break my regular broody mommas if I can't find hatching eggs or freshly hatched chicks for them.
Garden tending is the perfect job for your old hens. They eat weeds, scratch up the roots, eliminate pests, and fertilize and aerate the soil as they go! You will have to come up with a way to keep your fowl away from your veggies, though. There are some great, garden-row-sized chicken tractor plans on Pinterest, or you can come up with your own. I am working on plans for my own row tractor to use this gardening season, since it tends to get away from me after a while and it turns into a jungle. I'm also planting my garden lengthwise rather than across this year so that I can move the tractor up and down the rows more efficiently.
And, every now and then, a chicken comes along that has a very special personality that saves her drumsticks. When I was a kid I had this lovely, huge, barred rock hen named Roxy. I wouldn't let her get chopped, and I even painted her toenails red so I could keep her apart from everyone else. Now its my white Cochin, Oatmeal, who has hatched lots of new babies and survived being mauled by a Chihuahua, and of course Kahrl, a blue Cochin who is extraordinarily fluffy and who has raised new babies when other hens abandoned them. My husband's buff Orpington, Cornflake, probably won't be found on the dinner table either, since she is abnormally friendly.
An old hen's working days aren't always over after her laying days are over. She pays her rent in new ways that might even be more productive than before.