I have had my fair share of thin locks, mostly from hair loss at the edges after intense re-tighten sessions. Once the hair starts to grow back and grow longer I am faced with a dilemma similar to Kreyola's... Should I or Shouldn't I cut them off. I have made the decision on a loc by loc basis to cut them off for aesthetic reasons. Sometimes the loc is hanging by a string and thick at the root, again ruining my overall look. So then I cut them off as soon as it grows long enough.
In instances where the lock breaks off, my new consultant has successfully re-attached them as if nothing has happened at all! But we all face thinning or locs that break if we stay loc'd long enough, including those with traditional locs.