Put several of them into your onstart if you want it to walk a specific path. For example, if you wanted it to walk through pathnodes 1 through to 4, you'd have:
void OnStart()
AddEnemyPatrolNode("servant_grunt_1", "PathNodeArea_1", 0, "");
AddEnemyPatrolNode("servant_grunt_1", "PathNodeArea_2", 0, "");
AddEnemyPatrolNode("servant_grunt_1", "PathNodeArea_3", 0, "");
AddEnemyPatrolNode("servant_grunt_1", "PathNodeArea_4", 0, "");
The grunt will now walk through path nodes 1-4. I think there's another way to make them dissapear after they've walked their path, but I just tell them to walk to a node placed inside a collide area as their last path node which sets them inactive.
Answering your question though yes, I think they do just continue back and forth along their path then eventually vanish if they don't see the player, though I'm not sure of this.