I personally keep all my chickens until they pass away naturally. They are my pets. Some chicken owners cull their non-layers and replace them with chicks. It’s a personal decision.....
Good luck!
Breed them for chicks.
Bread them before cooking.
Sorry, couldn't resist playing on the typo.
I eat my old hens, they make great soup/stock, usually around 2-3 years old.
Depends on how many I've hatched that year, only have so much winter space.