This is a management decision. If eggs, eggs, eggs, is what you want, have the light come on a 4 am and go out at 9 pm. That is just about the maximum exposure required. A 4x4 coop wouldn't need more than 40 watts and can get that from a mini-flor cheaper than an old fashioned bulb. Do consider the bulb breaking and how you'd deal with the safety issues there.
Now, allow me to share what we do. We don't wish to be without eggs in the winter, as we have a solid customer base. To achieve winter laying, it begins with the proper winter hardy, winter laying strains and breeds. Second, I accept a 25-30% decrease in production for the winter as normal. I carry more hens through the winter to provide adequate production. I do not push my hens in the winter, as they need their energies for staying warm. Our wake up lamp comes on at 4:30-5:00 am.
It snaps off at 4:30 in the afternoon, because at the bottom of winter's light, it is dark here at 5 pm. I don't want to plunge them into darkness, catching them unaware.
I find that 11-12 hours of light is plenty to maintain fairly good production. Again, this is a management decision.
