So glad you have faithful broodies. That is such a blessing. Mine would be better, but I already hatched this year with my first gal, and the later hens' persistence encouraged me finally to think bigger. I knew I risked over extending some, but fortunately have others just coming into set so can flex a bit.
As to length of laying years, it really depends on breed genetics, care, and individual bird.
All my commercial red sexlinks are pretty played out by 3 years. My breeder quality birds have been less prolific but overall longer laying. My California Grey, a commercial hybrid breed, has been an awesome layer, but at age 3 her egg quality is now poor.
I like the longevity of breeder quality, so I have been breeding for color and hybrid vigor for a more sustainable flock hoping to average more of 4 years productivity with reasonable laying.
I have barnyard mutts now, due to that, but they appear to be sustaining better...but I'm still only a couple of years into the project.
Some have claims of 8 to 10 years life span, but that is not the norm in my experience. Those aged lay infrequently.
Generally it is 3 years of best production with larger eggs but slowing quantity by age 3 to 4. How much beyond that is genetics and care.
Longevity has been greatly skewed by the commercial industry's selectivity for very high production then cull at 2 to 3 years of age as that prevents a lot of med need in closer quarters.
LofMc