Unfortunately, this rarely happens that way. Production breeds rarely just stop laying and then potter off into senility. Due to their high reproduction, they often develop reproductive issues as they go out of lay, sometimes reproductive cancers(especially the ones who have had a light shoved up their butts all winter to encourage laying), etc. This is why they are usually culled at the 2 yr mark and replaced.
Not to say they can't last longer...I've had some still laying pretty well at 3 yrs but it's only a matter of time. Who wants to wait and see how they do and if they possibly suffer from laying issues and have to be given a mercy killing?
If you want breeds that lay great but are still standing in your yard past 2 years you will need a good DP breed known for exceptional lay. Here's an example of what I mean and YMMV according to your husbandry methods, so don't expect the same, but I can tell you about my experiences with the difference in production breeds vs. DP breeds.
Say a production breed lays 360 days out of the year(and that is about as high as it goes for any bird) but burns out in 2 years time. This equals 720 eggs if you bought them at POL. If you raised them from chicks, this number will be around but not exactly, at 570 eggs for their life.
If you get a good DP breed who will take a break during the winter months of maybe 2 1/2 -3 mo.(let's make it 3 to be safe) and it has to first be raised to maturity(usually a month or more past the age of the production hen to get there), her first year she will lay approx. 180 eggs but her second year you will start getting 210 eggs for a total of 390 by her second year.
Doesn't look like much compared to the PH who will lay 570 in her 2 years compared to that measly 390, does it?
But say your DP is still producing at 4 years? She will have laid 1020 eggs.
At 5 years? 1230
At 6? 1440
Of course, her egg production would not be 210 by the time she reaches 6 and could only be 170 per year or even less. And getting to 6 years of age and still be laying? Has to be an exceptional breed.
I've had BAs at the age of 7 and still going strong and I never got to see how long they could have continued because a couple of young pups I had got a hold of them. Who knows what could have happened?
Do I think my results are typical? Probably not. Possible? Yes. Depends on the breed and how hard you try.
Even if she lays to 4 yrs she has outdone the production hen and you will still have a meal when you cull her. She just might have gone broody each year as well and turned out some more of her genes, which you will not get from the PH.
A good DP breed saves you time and money way past what a production breed can do and I found that out years ago and have been acting upon it ever since.
The added benefit that has nothing to do with money? You get to have a pet that is also food and one that you will know like the back of your hand. You will be glad to give her the best gift you can at the end of her life. You can give her a clean death instead of one that involves declining into illness, pain and debility. In other words, you can eat her when she stops laying and feel good about giving her a long and happy life. You'll be able to point at the flock and say "There's Bertha's first girls and her grandbabies and her grandbaby's babies". She'll live on.
Of course, by the 4th year with a DP, you could have another 570 from another PH to total 1140 eggs in 4 years compared to the 1020 of the DP.
The replacement of production hens each 2 years is still going to yield more eggs but there is the chick purchase to consider as extra cost for replacement of that hen.
In 2 yrs. the DPH could have made up to 4 replicas of herself , so she has paid for herself not only in eggs but in 4 extra roosters for meat and 4 replacement hens.
Of course those are all theoretical numbers and a lot of supposed's but you get the general drift of where my mind has taken me over the years. If I were selling eggs for income, it would be wise to choose the PH over the DPH~ but most of us backyarders are only selling eggs to defray feed and management costs, while feasting on eggs and meat as another form of savings in the pocket.
What do you think about feed cost comparisons? My PH seem to be more feed thrifty and far better foragers than some of my larger DP birds. I know that following your culling calendar & requirements, I would be eating the less thrifty birds come March, and I may well be. I'm just wondering if there is enough of a difference to consider the cost of feed as well in this equation? Even with the cost of buying new chicks every two years, I wonder if the cost to feed PH is lower? Possibly Fred would have been able to chime n on this since he keeps his flocks of ISAs, utility, and heritage birds separate. Assuming they are fed the same feed, is there a significant difference in consumption among the three flocks?
I'm really just playing a bit of devils advocate with that question. I'm leaning towards a project of creating my own utility flock, using your culling schedule & requirements, Bee. I still don't fully understand chicken body shapes, lol, but I'm really looking forward to learning more about that in the upcoming Chicken U hosted by the OT profs . I, too am ok with the decision to wait until January, btw.
Finally, I bolted something you said about giving your girls a good death. A friend is going through the internal battle if deciding when/if to put down her 12y/o beagle. People and their dogs make me sad. I feel it is our duty and our privilege as dog owners to give them a peaceful, painless death. I get upset at the selfishness of some of these "animal lovers" who feed their pets pain killers and liver/kidney-killing meds for the last months (to years!) of their miserable lives. They cannot put the dog down bc "I don't know what I'll do without him/her." Boo hoo. It's your JOB to ease his suffering. He's been a faithful, loyal companion for over a decade. He's brought you many a smile. He does not deserve to be in pain. Quality of life.....
Anyways, I can relate to giving the chicken a long happy life and then ending it swiftly and calmly. No painful reproductive diseases. No egg bound hens. No heart attacks on the roost, although I suppose that is the more peaceful of these ways to go, the meat wouldn't be useful.
Thank you, Bee, for always striking a chord and putting chickens into a perspective that I can relate to.