Yes, adding a few hours of light is a hot topic. I don't do it, but only because I get enough eggs for us anyway. One aspect of it that is not debatable is, chickens have a set number of eggs for life, so if they lay more in winter, they won't lay as long. Truth is, though, many chickens die before they run out of eggs anyway. I've never seen anything in print that actually proves adding light is hard on them. As far as I know, it's just an opinion or feeling that a lot of people have. Not likely to be researched since commercial operations don't care.