Chicken life spans was one of the hardest topics to find any good info on when I first got poultry because, until recently, how many people really let their chickens live out their lives until they dropped dead of old age?
Anyway, that said, I now expect 8 to 12 years for a good basic dual-purpose breed or mixed-breed and heritage-style layers...maybe 5 to 10 for well-bred bantams...only 2 to 4 years for anything designed and sold by a hatchery primarily for commercial use. My current brown-egg layers are commercial hatchery birds. They don't even have the dignity of a proper name or number, they're just generic brown-egg layers designed to live 18 months, and because of that, I think they'll be lucky to see another summer. Which is sad. On the other hand, my longevity champion to date lived 16 years, a little Polish hen, and was healthy to the end, even pumping out a dozen or so eggs her last spring. So, lots of variation out there when it comes to chicken life spans, depending on what you get. Hope your amber links fall into the 8 to 12 year span.