It depends whether or not they are LUCKY. Hens on a mass production egg farm can expect an unpleasant one or two year lifespan before they are brutally slaughtered. Not a rosy picture, but wait, it’s even worse if a chicken hatches as a rooster. He will be granted only five or six months before his life also comes to a screeching halt. One may be somewhat luckier than the other… but quite frankly I’m not sure which one.
Backyard chickens can live eight to ten years in an ideal situation. Meaning, quality grub, green fixin’s, fresh water, shelter, and space to exercise their instinctual behaviors. Of course there are always chickens with that special gusto for life who continue scratching in the dirt far beyond the norm.
The older a hen gets the less eggs she lays. Her production cycle may even cease altogether. But this is just a part of their change of life, same as ours. Chickens grow old, but but let’s not overlook their other valuable ageless contributions. They provide an endless amount of fertilizer for your garden, eat ticks, flies, mosquitoes, and the creepy crawlers that destroy the foliage in your yard. Chickens are hard workin’ bug eating machines that are quite happy to earn their keep… at every stage of their life.
Dual purpose chickens are classified as birds raised for meat and eggs, seems to me the definition is lacking another option.