I was looking up information on Black Australorps and found out one of them, in the 1920's, layed 364 eggs in 365 days. Most book answers are for prolific layers to lay upwards of 240 eggs each of the first two years then taper off. There are so many variables affecting egg production, light, sickness, feed, age of the hen, etc that its tough to pin down how many eggs you can expect.
It is a known fact that all hens start to reduce their egg production by their third year. That's the reason commercial egg producers cull their hens prior to their first or second molt. That said, my two 'senior' hens are going on six years old (a buff orphington and a barred rock) and each of them produces two to three eggs a week. I read a post on this board last year, I believe, where someone had a ten year old hen that laid one egg a year.
My girls are all named (i.e. pets) and their quantity of egg production is purely secondary to the fun of having them around.