Bradley Hindman
Explorer
I prefer to adjudicate morale as the DM. Players would not appreciate me saying when they lose morale, why should an abstract rule set do so for NPCs?
Usually, there is a point in any combat where it becomes apparent (to me at least) that even if the enemy wins, the victory will be pyrrhic. At that point, I will either just have the enemy run for it or if I am uncertain if the enemy would realize the state they are in, I have the enemy make an Intelligence saving throw usually with a DC 10. Quick, simple, and imminently flexible.