Replacing an entire chain on the side of the road is not a difficult repair. One option, if your type of riding warrants it, would be to carry chain pliers, a spare chain (perhaps already cut to length), and a couple of quick links whenever you get over a couple thousand miles on your installed chain. Alternatively, you could carry a little piece of chain to splice a break.
Personally, I ride 6/7/8 chain. I carried a spare chain all the time for awhile, then quit because I never needed it.