Before I get into the 'fleeing' part, let me bring up a similar issue I have seen players grumble over: use of healing potions.
Yeah, same here - it's silly for intelligent foes to not use all the means at their disposal, and if the adventurers want to get hold of expendable magic intact, then that should be reflected in their tactics.I have always assumed that if the NPC has healing potions then they will use them.
Ditto for scrolls, wands, etc..
Unless a potion is in a chest or otherwise not on the NPC's person then *Gulp!*It is why they have it.