Lazy asks, " I am not used to having chickens so long... What do you do with them when they start to slow up on laying? Soup?"
I believe there is some technique for renewing their egg-laying capacity--the chickens are left hungry (fasting) for several days, which leads to their shedding their feathers. Then they are fed normally again, re-grow their feathers and return to full speed laying.
Try looking it up in the literature (Wikipedia?).
I'll try to find out the details myself too, and pass the word on to you. It's certainly better and faster than starting with chicks again.
However, in general, during the short winter days, hens naturally reduce their egg-laying. The shorter days influence the necessaary balance of hormones and laying is reduced. In Israel, probably elsewhere too, egg producers turn on lights in the chicken runs during the night, to artificially imitate the effects of longer days. When longer days return, egg-laying picks up on its own.