Once only. One of their narrow-necked, (rather than wide mouth) bottles broke its neck when I stupidly dropped the thing. I didn't think such lexan material should break, and in one email I called their attention to it. They sent me a new one. I can't remember if I had to send the broken one in. This was probably 4 or 5 years ago.

Like many others here, I've stopped using my Nalgene jars for hikes or any backpacking. I still use them heavily for taking to work, (I work outside,) car or truck tent camping, and around the house (I'm a very heavy water drinker.) But in my thread about all water containers, I was educated by this board about other ways to carry water in the pack.