Gosh Darn Monsters [spoilers]

[GraphicsKid]

The wait it works is when a monster is spawned, they are assigned a bunch of "patrol nodes," or spots they are told to walk to. Yea they'll deviate from those paths if they see you, but otherwise they'll walk from one node to the next, and when the reach the last one, if they're far enough away and off screen, they'll disappear.