Hi there,
Its a question I get asked regular, but to be honest I don't know the answer as I rotate my hens. I find after the first year of laying egg production will drop sharply. I don't see the point in keeping hens that are not producing so they end up in the pot and I have a new flock waiting to take command of production. I know people who have had the same layer hens for years and complain they don't get eggs. I give the above advice.
Of course layer hens give a more concentrated delivery of eggs unlike some other breeds which will spread the laying over a longer period. Also take into account conditions such as weather/ season as this will affect laying and you should be able to make a sound valuation before making a decision.
ciaou