For example, in the Lava Caves, if you drop down the right side from the main bridge to the north. There was often a circle of power and purple crystals here.
If there is a circle of power before the sliver of lava and you run the line, to the east without a teleporter. After about 2 1/2-3 torches they would collect crystals and then try heading east to climb the ramp and path all the way back to the center.
However if you run the line west and the north into the sloping down ramp, once they collect they still have "forgotten" about the teleporter. They just happen to head up the ramp and then go east to follow that same path up to the center. The teleporter happens to be in their way so they will then use the teleporter.
Another case in point in the Lava Caves. Go to center bridge and FF to the other bridge down to the west/left. If you drop the line from the circle of power north along the bridge they will turn around heading towards the teleporter. If you drop the line south up the spiral ramp, after 2-3 torches they will continue heading up the ramp.
So when they use the tele when running the line north they only use it cause they run into it on the way back up the spiral ramp since they have "forgetten" about the teleporter.
This is something I have always had to keep in mind when dropping a line, and considering a DD or 2nd teleporter before I string out a line too much.
The kobolds have never really run in the "shortest path" but they are always looking to get back to the center/foreman. I think they go to teleporters only with line of site, which considering how short the site is for cyrstals they seem to be very short sited.
Maybe it is time we have the option for a glasses powerup or buff for the kobolds. =)