We've got two groups here, the "named" and "the chickens".
The ones who have earned names get a lifetime pass. A name here isn't like Nancy or Lulu, we have "the friendly gang", "runt", "toe biter", "ugly", "the one that isn't ugly", and other similar identifiers. If your personality stands out enough that we can immediately pick you out of a crowd, you're a pet.
The chickens who are just a part of the herd of chickens, well, we're a little less attached. They fall into 2 groups- the ones we don't particularly like, and the ones we just didn't get attached to. The first group is flighty, bossy, loud, and not at all pet material. When they stop laying, they won't last all that long- mean freeloaders aren't that fun, and I'd rather have productive birds I actually like. The other group will get to retire here, but if they get badly hurt or seriously ill, they'll be culled, instead of having me bend over backwards like I would do for the named girls.