there is absolutely a reason to kill your chickens that aren't laying - it costs money to feed them. if you don't optimize for price by slaughtering your older hens you will easily be paying > $10 a dozen for eggs.
all bets are off though if you consider chickens pets, instead of livestock.
basic economics for me: 20 chickens, a dozen eggs a day, 30 dozen eggs a month. decent non-organic feed is $20 a bag, organic is $35 a bag. one bag per week if you have the space to do daily free ranging on a decent sized chunk (half acre chicken yard in my case). Round up $0.50 per dozen for incidentals (bedding, repair, replacement chickens semi-regularly due to predation). That's $3 a dozen for non-organic, $5 a dozen for organic.
Drop productivity in half, organic eggs start costing $10 a dozen, and you have to work for those eggs. Cut productivity to 25% and you are even more expensive. In my experience, you are at 50% productivity within 3 years depending on the breed.
Also slaughtered old hens make good soups :)
all bets are off though if you consider chickens pets, instead of livestock.
basic economics for me: 20 chickens, a dozen eggs a day, 30 dozen eggs a month. decent non-organic feed is $20 a bag, organic is $35 a bag. one bag per week if you have the space to do daily free ranging on a decent sized chunk (half acre chicken yard in my case). Round up $0.50 per dozen for incidentals (bedding, repair, replacement chickens semi-regularly due to predation). That's $3 a dozen for non-organic, $5 a dozen for organic.
Drop productivity in half, organic eggs start costing $10 a dozen, and you have to work for those eggs. Cut productivity to 25% and you are even more expensive. In my experience, you are at 50% productivity within 3 years depending on the breed.
Also slaughtered old hens make good soups :)