When to retire?

[ChickenCanoe]

I don't think there is a great deal of difference in the tenderness of meat whether a bird is 2, 3, 4 years or more. By 2, they've been using their muscles a long time. The meat will be firm and flavorful. Teeth will be needed to eat the meat and it will need to be cooked low and slow. A 4 year old bird won't be any tougher IMO.
If you don't want to feed chickens through an adult molt without egg production, you need to rotate them more often and have a lighting program. You'll need to bring in new birds at least annually or ideally semi-annually. Bringing in chicks hatched by February will have them laying by summer solstice. Chicks hatched after that will reach POL after summer solstice so without a lighting program, onset of lay will be unpredictable.
While I like productivity, my goals are different. After over 30 breeds, I've settled on a single great breed and my goals are to get them more widely recognized and improve them. With that in mind, I let my good hens go through several molts and often have hens laying for 7 or 8 years. I'm still getting the genetic output even if annual production may be half of what it was when they were younger. What I do know is that (without a lighting program) they resume laying a short time after winter solstice and usually lay like gangbusters till late summer.

 

[FarmerGirl101]

If you are looking for profit. Check out leghorns as they can lay year round without light.

 

[Dr.GarryTTucker]

Excellent write up as usual.
The good doctor (OP) hasn't noted what breed/s he has. That will be a critical factor in the discussion. If consistent egg production is important, one must choose consistently productive breeds.
That wouldn't include silkies, cochins, brahmas, houdans, games, nankins, etc..
Instead, perhaps get some egg hybrids or if wanting heritage breeds, I'd choose RIRs, Leghorns, Minorcas, Dominiques, Anconas, Australorps, Hamburgs, Redcaps, Sussex, Jaerhons, Fayoumis, Plymouth Rocks, etc..

I have all Rhode Island Reds and 3 Buff Orps

 

[aart]

I rotate my stock kind of based on winter space.
Neither I nor the birds like a crowded coop in winter.
I hatch chicks every year in late winter.
Cull (selling or gifting or slaughtering) all males by 14-16 weeks.
Older hens(~18-30mo) are culled before hard winter hits.
I do use lights for winter laying, not always effective,
it's not like flipping a switch-haha!
In 5 years I still don't have a 'pat' system,
gotta be flexible as the situation dictates and as I continue to learn.

Did real well the first few years, covering all feed and bedding costs with egg sales,
but now am breeding Olive Eggers with Marans and CCL...neither are great layers.
But I still have plenty of eggs and meat to eat.
Who knows what this next year will bring<shrugs>

 

[Morrigan]

Some hens are just haler and more productive then others. I've had 4 and 5 year olds that were very productive and others that declined dramatically after 2 years. I like keeping those older, but still very productive, birds around because those are the eggs I want to hatch. Older birds can also have value as broody hens and flock leaders.

It's been a hard process for me, because I get attached quickly, but I've gotten better at removing hens for poor health and productivity (and I've found the two go hand in hand). For hatchery stock birds bred to lay lots of eggs, I've found that by the age 3, anywhere between 25 and 50% will start having reproductive problems, and are obvious culls.