When I lived in a big city I had an in/out cat that lived to be over 12. I'm sure he would have lived longer but he had kidney failure. He never brought me birds and was obviously savvy about traffic. Most of my cats lived at least 10 years. Our current cat is at least 12 but we're not sure exactly, she was an adult when we got her. She has a thyroid issue so we know she won't last too much longer, but she is not dying. She's a good mouser and has brought in the occasional bird - but generally she brings them in unhurt, just to show them to us. One of my favorites was the American woodcock, we never would have seen one if she hadn't brought that in. Google it, it's an odd-looking thing.The well- fed domestic cat is a great hunter. Having regular meals gives it the energy to hunt. And they rarely hunt to eat. They hunt to keep their skills sharp. And bring it home to feed its 'family'. Average lifespan is 6-8 years because it is dangerous out there. Cars, dogs, other cats, wild predators, dangerous chemicals, and creepy people. Parasites, infections, barbed wire.
It's hard to be a cat.