The Guinness World Record for oldest chicken is/was held by Matilda. 16 years old!
Just like any other pet, chicken age will depend on their care.
How long will chickens lay eggs for?
Chickens molt at about 18 months of age.
Molting is where they lose all or some of their feathers and stop producing eggs for a few (2-4 months).
This is a natural shedding of feathers.
Factory farms usually cull their hens at this time, BUT if these are your pets you don't have to cull your hens.
They will continue to lay eggs after their molt, until they die (hopefully, like Matilda at 16+ years old!).
They may not lay as well as they did during their first year, however they will still be sweet and cuddly pets.