Hens are most productive the first year they are laying eggs. After that first year production tapers off. While hens continue to live for several years, the produce fewer eggs per week. Most commercial productions therefore only keep young hens, constantly rotating new stock through their facility. (By the way, I'm not sure what happens to these hens. At that age they are too tough to become roasting birds, and most layers aren't considered suitable meat birds anyway.)
We currently have two older hens, a black Australorp and an Ameraucana. The Australorp has black feathers that have a beautiful green sheen in the sun, while the Ameraucana fits right in with our mature Ameraucana chicks. We know that we average an egg each every 2-3 days, as long as there is enough daylight, while our newly matured hens are laying an egg a day. To keep production high, I intend to add another five or six chicks each year.
This year I'm adding silver-laced Wyandottes to our flock. These are the same breed as my rooster, except that he's a gold-laced variant. These will be medium-weight birds, meaning they have a medium-sized frame, and will lay brown eggs.
I was lucky enough to get an unused brooder from a friend, so this year's chicks are living it up in style. The brooder has a wire mesh floor, which allows droppings to fall into the shaving material in the tray below. It's also equipped with a heat lamp and thermostat, so the chicks are kept at a toasty 90°F. They can self regulate by their position in relation to the heat lamp and have free access to water and chick feed.
Each week the temperature will be reduced by five degrees, until around four weeks when they have grown feathers over their baby fluff. At that point they have enough body weight, mass and feathers to withstand drafts. Normally a mother hen would be the primary heat source, hovering over the chicks and keeping them warm with her fluffy underside.
With the Ameraucana chicks, our old red hen, who passed away several weeks ago, took on the role of mothering the chicks. Granny guided them around the yard, protected them from the other chickens, and taught them where to eat and drink. For several weeks the chicks still came in at night, and she would wait for them to be brought out each morning. I don't know if any of our current hens will show mothering tendencies now that Granny is gone, but I hope so.