We had a couple EEs that were 10+ years old. They laid every 2-4 days until last year. 1 of the sisters started laying shelless eggs. She ended up becoming an internal layer and had to be put down when infection set in. Once she was gone, her sister stopped eating. After several days she was skin and bones. She got so weak we sent her to be with her sister. She refused to eat and would not tollerate being force fed. They had been together since they were chicks.
I have some 4 year olds now that lay well when it is not so hot.
Some of my girls are 6 years old and they still lay.
My friend had a hen that lived to be 15 years and that hen laid about a dozen eggs a year at that age.