I think alot depends on the breed and individual chicken. I have read about people on here that have 4 and 5 year old chickens that lay fairly regularly.The older a hen gets, the larger her eggs get as well. I have heard that older breeds will lay longer than newer varieties. But this is all hearsay!
We have Dominiques that are around 7 yrs old and they still lay every other day!! I didn't know that there eggs get larger as they get older. That would explain why the eggs don't fit in the egg cartons!!
Our hens just started laying and their eggs are little still. The guy at the feed store told us to make sure that we had them all laying before we started giving lay pellets. He told us that if we give them to soon they will lay for a shorter period of time