A friend of mine swears that her parents have two Cornish Rocks who are excellent laying hens. She says they not only lay eggs several times each week for the past year, but that the eggs are almost always jumbo double yolks. I'm new to chickens but from what I've read, Cornish Rocks aren't event likely to live to maturity if they aren't butchered for meat by 12 weeks or so. So is it possible for this breed to be kept as good laying hens or is my friend probably mistaken about what kind of chickens her parents have?