I agree. I did have a cat that came to me. It showed up on on my property (of rather small size) and wouldn't leave. When the weather got nasty, he would come in for the night, but would sit at the door until we let him out, and if we didn't his cries got progressively worse until we did. He was just too used to the part inside/outside life. Before he showed up, we had a serious mouse and rat problem. A few months after he arrived, no more problem. I literally never saw any evidence of rats/mice again (5+ years until we moved).
The mice were getting to be a problem, btw, because they were burrowing between the walls of my house and making noise at night, and doing god knows what damage in there.
My wife was once on the porch with him. She was gardening (lots of potted plants, etc). He was laying there in the sun and snapped up to grab a hummingbird in flight. She grabbed him and he spit it into her hand. The hummingbird flew away a few seconds later. That was when I realized how efficient a predator he was.
EDIT: and he did get into a fight with a raccoon once, that required stitches. So, living inside will definitely increase the health and length of life.