FWIW, our flock of 8 (7 4 years old and 1 9 years old) was still giving us 6 eggs a day in the height of summer this year. They took a break for molting in December and then the eggs returned starting in January, right though a cold VT winter. We could start selling extras again by mid February. We found a home for the 7 4-year-olds (we weren't going to have time to slaughter them this year) and kept the 9-year-old Henny Penny as a pet, assuming she didn't lay any more. Boy were we surprised to discover that she still lays an egg every other day!!! like clockwork. Not the hugest eggs, but she goes into her favorite nesting box every other morning and gets the job done. She's a big Buff Rock, still looking good at 9!! So it all depends on the breed, how much range and food they have available (our birds have a big netting fence that is moved weekly and lots of kitchen scraps in addition to their feed, plus corn in winter since there's no heat in our barn and it gets COLD).