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Hens have been bred now that lay 100's of eggs a year; and they don't seem to miss the nesting instinct. Food goes in one end and eggs come out the otherRather unnatural in such quantity, but the hens seem contented enough. I have a lot of friends who keep free range chickens, there's no shortage of eggs.
Going to disagree with some of this - hens do still naturally try to hatch eggs - its only the act of daily egg removal that keeps them laying - its a completely natural behaviour. They are constantly trying and failing to complete a clutch. Let them complete that clutch and they will quickly go broody, try to hatch the eggs (and succeed if a cockerel is present) and stop laying.
Chickens live from six to ten years - but almost all egg laying birds are killed at two years as after that they cannot keep up the egg laying speed and the economics don't work - so they are slaughtered (and almost invariably not eaten as they are not nice tender meat birds).
Its a funny old world where the things like dairy and eggs are, to my mind, the cruellest parts left of farming - rather like the growing of vegetables causes the greatest destruction of nature and wildlife.
Still, far be it from me to argue with food choices - some people eat brussel sprouts - I'd rather have a cheese omlette any day!