I've been using the same chain, but only for 150 miles. The only problem I had was when I put the link back it took me a lot of effort to get the link to loosen up.

I only carry enough for a two tube changes and my ID, health insurance card, and credit card. Sometimes I carry cash (which was useful one time when I had to boot a tire). I was thinking that if I get in a really bad situation I always have my cellphone and could call someone.