Something occurs to me..... We all do care about our chickens and we all, at some point will deal with their passing.
For me the decision had to be made before the chicks came home. I am a planner too.
I am actually ok with processing them for food. We eat chicken... eating the ones I raised means not supporting commercial housing and the meat bird industry.
This does not mean I care less for the chickens just because they end up dinner. In fact it is a motivator to make certain mine always have clean water, good food, proper shelter, treats and the best life I can give them.
I have lost a few unexpectedly with no warning signs. I have had ones get sick and show symptoms. The ill girls go to the vet for a humane end and exam. The vet charges me only 25 to put one down and do a very brief exam.
The ones that dropped over were very young, under a year. Two were from egg binding, another from a weak heart were the root causes. The ill ones were between 4 and 6 years old.
It is a very personal decision for each of us. Why??? Because they are in our care and death is not an easy decision. If it were easy for us we may want to do some self assessment.
There are birds in my flock that don't lay well or at all but are adored for their other qualities. I keep mine as long as I can logically believe them to be having a happy life. That means my hens bred for laying are here for about 6 years. Can they live longer?? Probably, but I choose not to wait for them to get sick. Personal choice.