I had a battery that was ten years old and still going strong up until I replaced it late last summer. They usually fail when the weather changes and I'd rather replace it before it dies cuz you know it's not going to quit in a convenient location.

I also know of another battery that was close to 10 years old that was replaced before the car was used on a long road trip. Figured it was old enough, and they more than got their money's worth out of it.

I have an Interstate battery in use right now and so far it's fine.