I have Brahmas. Most of my flock is 6-ish years old now. I am still getting eggs from all of them, just not every day. Out of 12 or so old girls, I'm getting probably 6 eggs daily. The younger girls are laying more, of course. Frack, who is 6+ years old, still comes in the house to lay her eggs. She usually lays about 3 days in a row and then takes a week off. Our oldest chicken is an unknown breed bantam, just over 7 years old. She lays faithfully every day when she isn't broody; however, she is broody most of the time. As we speak, she is on a nest of 5 eggs due to hatch the end of next week. Another Brahma, Buttercup, lays every day but hasn't had a fertile egg in years. Today I candled the one egg of hers that I put in the incubator - it's developing!
None of my chickens are hatchery. With the exception of Chrissie, the bantam, I have raised all of my flock from eggs.