That's what happens when you let them feed in nature and just use a bit of supplement feed, real 'free range' style.
Of course the problem we have is too much population to meet demand like that. I think we can find a controlled flock, free range solution that everyone can agree on in price, production problems, and ethics.
The issue is not so much the one of 90-120 life cycle then going into the pet food market, that's perfectly fine in the natural order. What is mostly in question is the quality of life of the chickens for those 90-120 days; "Do we cause them a life of torture and suffering?" This is the primary issue as I see it. There was an interesting guy on Mary Gross the other day discussing this very thing. He said the chicken is the most prolific animal on the planet and they, and bovines, have been the most abused species by man on the planet.
I think a controlled free range model that maintains defined flocks with indoor and out door habitats where they can have a reasonable mindless life of a chicken with some semblance of autonomy for those 90-120 days with reasonable methods of dealing with the facilities.
The problem doesn't really stem in that we use life, the problem comes in the abusive, thoughtless way we treat life.