The Cornixh X is the Gold Standard for the meat chickens. Butcher at 42 days for 1-2 lb game hens... at 6 weeks for 4-5 lb friers... at 8 weeks for 6-8 lb friers... or 12 weeks for 8-13 lb roasters. These are carcass weights, not live weights. Those birds from JM hatchery will take at least 2+ weeks/ or more and they may/ or may not reach those weights. Today's dual purpose breeds will take 18-20 weeks to slaughter, however one would harvest a carcass that will be 3 1/2 - 5 pounds. Keeping them any longer and one will have a tough old bird with still a small amount of meat to eat. Spent egg layers are best used for chicken soup. One would want to educate oneself as to the protocol to raise them successfully... limit the Cornish X 's food after 3 weeks of age to 12 daylight hours full fed and without food for 12 hours at night as otherwise they will grow so fast that some chicks will develop leg or heart problems and may die. One may want to raise them in a tractor ( rather than a chicken house ) and move it daily as with great amount of consumed food will yield a great amount of excrement and odors associated with it. Some say that the dual purpose chickens have more flavor. Flavor comes with age due to additional time to deposit FAT. I found that by adding top dressed with cracked corn to their normal feed for the last 2 weeks will add the extra fat needed for that flavor. Then too, One will find from experience that it is much less expensive to purchase a day old Cornish X chick than raising one's own dual purpose breeder flock, incubate the eggs and then raising those chicks to slaughter. I raised Rhode Island reds, New Hampshire Reds, Barred Rocks, and Leghorns and various crosses thereof for decades untill 3 years ago when I discovered the cornish X. Now I order my Cornish X chicks , raise them for 6-8 weeks and then invite them to freezer camp, I can enjoy the rest of the year care and worry free. The dual purpose or Heritage breeds are just too labor, feed, power, housing and time intensive for 365 day venture for their yield.