They can live and lay for 5-7 years if you don't use artificial light, and do every thing right. TwoCrows who mostly helps out in the new members section these days had a few that were more than 5 years old. 2-3 years is the average life span though, with egg production dropping off after the middle of the second year. Like QJ I usually turn over my producing birds every year. Not so much because of egg production dropping but because most animals will generate their healthiest offspring while in their prime and I hatch most of my eggs.
If you are concerned with having thrifty birds, I would change them out at least every 18 months.
If you are concerned with having thrifty birds, I would change them out at least every 18 months.