In my experience, once the first year pullets start laying in the fall, they lay pretty well thru that winter without light supplementation. It's the following year, when they often go thru a long molt in late summer and fall that they can really slow down or stop laying. I don't supplement light, my neighbor does, and she seems to think it helps. I've read in various places that it might be best to have a timed light come on early in the am, rather stay on longer at night, so that it doesn't suddenly go off before they are settled on the roost etc - the gradual fading of the light in the evening gives them time to get themselves tucked in. I have a coop with a viewing area and I love to watch this happening in the evening with all the clucks and coos, but it takes awhile, so that makes sense to me.