It is very normal for birds to get elderly at 3+ years. And really, if they are gone in the morning, well they have had a good life and a quick end. Personally, I like a multi generational flock. So when I lose some, I add some.
I have an older rooster too, and he is getting grumpy. Course he is also molting, I have a young boy growing up in the flock now, and come the spring, I may cull the older boy. It is the circle of life, adding and subtracting.
My granddaughter and I feel a bit sad, but not devastated when we loose them. Nothing new chicks can't help with.
People often times do have much older chickens, but I have never had them live like that. I am not doubting them, but don't feel guilty if yours don't live that long, a lot of chickens don't.
Mrs K