As far as I know, hens never STOP like forever -- they just lay fewer eggs as they get older. And the eggs they lay are larger.
Depends on the breed, the conditions she lives in, her age, her general health, etc. There is no set time. I do think, in general, she will begin to slow down toward the beginning of the second year of life, but will continue laying for years to come, if she is well. I have some who are four years old and though they have eased off some, they still lay several eggs a week when not molting. Someone here had a hen up in her teens (17, I think, when she died) who still laid an egg every so often.
most of my chickens lay consistently until around 4 or 5.... Then I often see a steep drop off in egg production. Even the old gals lay sometimes. A very old Speckled Sussex that I am not sure of the age of (I estimate her to be between 7 and 10 years old) because someone dumped her in my yard, layed very well until this year. Almost daily! What a chicken! I would be curious if any other sussex owners have birds that laid a long time like that.
