Older birds are often thinned because they don't lay as well as younger birds.Don't thin! They're not laying because they're spending their energy on staying warm, surviving the winter. The daylight hours they need, to keep laying, have shortened. It's seasonal, completely natural for them to not lay during the season where it would not be best for chicks to survive, if they were laying in the wild (chickens actually are a wild bird species that has been domesticated). The time for the chicks will be in the spring, for them to start laying again. This is completely NORMAL! Yea, they're being free-loaders for now, but this is common. So, don't thin your flock, thinking you can add later on, and then have to wait for the new chicks to come of laying age, which, again, would put you in a shortened laying season before they become free-loaders again for the winter.