First, it takes approximately 16 hours of light, natural, artificial, or a combination of both, for them to lay.
They lay an egg roughly every 25 hrs or so. Of that 25 hrs between eggs, 22 hrs is spent in the shell department. Some will have shorter periods between eggs, others will have longer periods between eggs. Oon average, when hens are laying reliably you should get 6 eggs per week.
Our hens lay 3 days in a row, skip a day and repeat. They have a minimum of 15 hrs of light per day, so we have eggs year round. Granted, our's is artificial, but it works. For those of you that do not give additional light during the winter, you will have lower production due to the shorter days. Once the days are long enough they should get regular with production.