The answer is; it depends. Generally many hens will produce fewer eggs each year, and to plan ahead, adding a few at least every other year will help keep your egg production better. Lights in winter, 4am to 8am, help to keep mature birds in lay, although there's nothing 'sure' about any of this.
If you plan to eat your birds and replace them every other year, always having some new chicks annually, that should maximize your production with the fewest birds.
If you keep at least some nice hens much longer, then you will have more birds, including youngsters, and that works too, although it's not as cost effective.
Many of us like our birds, and keep at least some of them for life. I value the broody hens, and the mature birds who teach the youngsters how to get along, and don't get rid of birds who have done good in my flock.
Mary