The listed life span is around 8 years but some layers burn out early at 2-3 years and others can exceed 8 years. Maybe one of the old hands will give you better info.
I have hens that are 6 years old now, and still lay eggs. My friend had a hen live to be 15 years old, at that age it still laid about a dozen eggs a year.
But seriously, we have had chickens on family farms go into their teens while others only live to 5 or 6. I have only seen one hen that was laying well into the late teens.