I carry a couple spare hinges in one of the pockets in my case liners. I had to replace one when I dropped my K75RT on a muddy Nebraska road a couple years ago. Took about 10 minutes on the side of the road to change it. I like to think that the hinge breaking saved the case when the bike landed on it.
Considering that these $6 hinges probably have nearly 25 or more years on them, and a couple thousand cycles, I can't really complain when one of them fails.