and if breeding (which is probably nearly impossible since they are hybrids) use the oldest healthy hen and the oldest healthy rooster of the parent stock to put some old age genetics in their little feed-conversion-egg-laying-machine bodies.
We've been using various sex-links in our breeding for years. But to back track, just one more time. The fact that a bird may be sexlinked does not, in itself, tell you a blessed thing. You could put a Heritage RIR over a Heritage silver/white bird and make red sexlinks. They'd NOT likely be awesome layers, though good ones, and they'd live as long and as normally as any other bird of their large fowl kind.
The term "sexlinks" conjures up a commercial, fast growing, fast laying Reddish Brown hen with white sub feathering. Those birds, in many cases, are commercial, brown egg layers and are to the layer world what the CX is to the meat bird world, in many respects. They've been selectively bred by the poultry genetics corporations for decades to be the birds they are today. It is these birds that primarily leap into people's minds whenever someone says "sexlink".
They were developed for a single purpose. Lay eggs. They aren't dual purpose birds. Grow quickly, enter POL quickly, lay lots and lots of jumbo sized brown eggs, tolerate very close living quarters, never go broody, and convert feed in an extraordinarily efficient fashion. That's what the industry needs and gets. Since the industry turns over their flocks quickly, how long they may live, in terms of 5-8 years, is completely irrelevant.