Maybe on here that it true, but the facts are that the "heritage" birds DO live and lay longer. A second? cousin of my Dominique's is 4 and still lays an egg a day. You'd be hard put to find a commercially bred bird do that. There are a lot of breeders that do breed for show only, but there are also a lot of breeders that breed for both, SOP and utility. The reason you don't see them as much, is that they are not on forums talking about it, they are simply doing it. Plus other agricultural things, like produce, or livestock and simply don't have the time to sit on forums and talk about it. I am glad we have this forum, as being where I live, so far, I have not met anyone near enough to me, that I can work with. So come to forums, like BYC to gain knowledge. The fact is, Heritage birds have lots of qualities that the hatchery birds do not. Better health, bred for immunity, longer life spans, longer laying ability, better tasting meat. and more of it.
The commercial industry has mixed and bred birds for one thing, take the cornishx for example, Yes, they grow quickly and are at slaughter much more quickly than a Standard bred bird. But that is their ONLY function and many have health issues like legs, runny poo's ect. The layers are good for 3 years tops then they tend to develop issues like prolapsed vents, eggbound and their health is fair, and egg laying slows considerably after 18 months, and they don't have the natural immunities. Now some of that could be solved by husbandry. Look at what Beekissed has done with her meat crosses and done successfully. But all in all, the commercial birds just are not a good back yard flock. IMHO
Could a commercial layer quality bird be a better bird if crossed with a "heritage" bird? I believe yes. Would you ever get them to the SOP? I highly doubt it. BUT if your goal is to produce just layers, or a true dual purpose bird, you simply cross the two types of birds and have a GREAT dual purpose/layer bird/flock with the benefits of the heritage bird in a few generations or so. I want BOTH, to breed to the SOP AND have the utility. They did it before, so no reason it can't be done again! and is being done again. Just not as publicly!
My Dominique's are a great example of that. They are bred to the SOP and have great utility in both eggs and meat. Do you see their breeders on here? I haven't much. Only on my state page, and not often. My point? One, that birds can be both and that it IS being done with the heritage birds. There are other points but that is the basic premise.