If you raise your hens in lots, say you buy 20 production reds, you can band them all in one color and then when production is down, kill the entire lot and replace it. This is usually the best way to go if you are dealing with a great number of birds. Traps nests work well for smaller flocks, just remember to go out several times to release the "trapped" hens.
I eat my older or extra birds. We have watched movies such as "Chicken Run", but in reality the chickens are not in the coop being "scared" into laying eggs because they fear the axe. I do not feel I owe my chickens a retirement into old age. I feed them great food as much as they want, I provide them with shelter from the cold and rain, they have ample opportunities to forage for grass and bugs, I even take the time to destress their sex-life by keeping the right amount of roosters with the hens, they have great nestboxes, and lead a great social life. LOL. Granted certain birds I get emotionally attached to and these may be given an exemption from the default retirement plan. I pay my hens very well for the "job" they have done providing me with eggs. When they are no longer laying like they use to and I need more room for newer birds, I give them the best death I can reasonably provide.
I do keep hens that have stopped laying but are prone to be broody. I did it with one of my Sexlinks lately. She's been dwindling off, it's her second year so she's due for a burnout. She recently decided she was going broody, so she may have a future in being a mother(if she stops smashing eggs!!
).
If you decide to eat, remember older hens should be slow-cooked/stewed, because they are tough.
If you decide to sell, don't lie about age. If someone asks, be honest. Most people buying full-grown hens assume they are buying layers and usually pay decent money. If you give them away as pets, same deal, make sure they know why you are giving them away.
Anyway, that's what I do/plan to do. You have many great suggestions here to work with, in the end it is your decision.