I haven't yet fact checked this so I don't know if it's true or not..... but someone on here somewhere said that leaving a light on for the girls in the winter can shorten their life span? Not sure that it's relevant to me since I don't reckon they'll survive the dinner table long enough to live to retirement anyway. Again, not even sure that's true. Maybe someone with more experience can provide further info on this.
Chickens are very photosensitive, and many need a minimum of 14-16 hours of light a day to lay well. More than 18 hours will actually slow down egg production, and light 24/7 will cause lots of stress and possibly cannibalism. All animals must have a dark period each day for their bodies to function properly.
http://umaine.edu/publications/2227e/ is a good discussion on poultry lighting for all stages of a bird's life.
I have not seen any research that shows that the chickens' life span will be affected by supplementary lighting, although here is an interview with an avian vet that says it does not:
http://www.the-chicken-chick.com/2011/09/supplemental-light-in-coop-why-how.html.
There is a possibility (I've not seen any research one way or the other) that the hens will stop laying at an earlier age if they have lighting in the winter. It seems like it is basically a choice between getting most of your eggs in the first 2-3 years or spreading that number of eggs out over more years. Hens, like humans, have a finite number of ova and so you can't make a hen lay more eggs than her body is hatched with. For those of us who keep chickens for egg production (not just as "pets with benefits") and replace them at 2-3 years, it ABSOLUTELY makes sense to use supplementary lighting.
I have some broody hens that are going on five years old, and they still look great even though they have supplemental lighting every winter. I have no idea how well they lay, as there's no way with my flock to really know who lays what, when, but that's not why I keep them around, anyway.
Anyway, whether or not you provide lighting in the winter seems to be a personal choice, dictated by economics (you willing to buy eggs all winter while still feeding hens?) and personal choices about the hens' lives (do you feel like the hens need a break every winter, for longer than their natural moult period?). My hens moult every fall, and get their rest then. As soon as I see them moulting, I turn on the lights for a bit longer every week until we're up to 15 hours of light. Most of my flock lays right through the winter, which pays for their feed. For me, there is no other choice. You'll have to make up your own mind.
After looking around here (byc), I found out about the fake egg thing so I placed a pingpong ball in the latest laying locale... So far, so good - she hasn't moved her nest since. 
