brake lines have to pass a DOT "whip test". They mount it in something and whip it back and forth so many times. Typical SS lines break at the joint. DOT legal lines usually have a plastic sleeve at both ends or I've seen some with a spring.
I've also heard you should replace them on a schedule since you can't inspect the condition of the rubber lines. My pedal is still a little long, but it has a pretty good feel.