The real, souped up egg layers, (genetically selected to be first generation 300+ per annum layers) are also typically bred to lay right through winter. Now, increasing the light to 15 hours a day, during the dark weeks before and after the solstice of winter, will cause them to continue to produce at near normal and normal for these breeds (hybrids) is 6-7 eggs a week.
Even if you provide no extra light at all, these hens will still lay 5 eggs a week, in most cases.
Some of the "these birds burn out quickly" beliefs are more legend than fact. I wouldn't expect them to continue this level of production and they do not. They go into decline in year two and continue to fall farther in year three.
If a small poultry farm operation, such as my own, has a rather fixed number of egg customers, the need for XX dozen eggs per week needs to be maintained. The simplest way for an egg producer to meet his demand is to rotate in chicks/pullets every six months, let's say, and also rotate out at similar time spans. Hope that makes sense.