It depends on the hen and how much the molt takes out of her. (body weight wise) Anywhere from 2-5 months.
I'm finding out chickens are not very dependable on laying eggs. I have six and they are seven months old. I was getting around 20 eggs a week at the peak in early October. Now I'm getting 7 a week. On top of that they stop laying if the wind is too bad or it rains too hard or if it snows. Now I have the molt. I may need to get more hens, is that the chicken math people are talking about ?