Chickens don't have a calendar luckily:) she will sit until you either break her broodiness or she hatches her eggs. I don't reccommend letting her sit much more than you are as it will be close to a month by the time her chicks hatch. Hens barely eat or drink while sitting so it's hard on them
Most hens if not broken from their broodyness will just continue to sit. Being she has no fertile eggs she is just waging a losing battle. Your best to just break her by putting her in a small crate or fencing her to keep her from getting into the best boxs every few days let her loose to see if...
I love a product called poultry protector. I get it from first state vet supply. Dr Peter brown is an expert in poultry and will always take the time to help if you have any questions. He has a website too. Poultry protector is non toxic so it won't hurt you the environment or the birds.
100% English Lemon Cuckoo Orpington cockerel 9 months old. Keep in mind he is still growing and filling out.He is truly a gentle giant, easily handled and a pleasure to have around. Please keep in mind he is a big guy and that you have adequate housing. He is molting his tail a little right now...