Well, to be seen by monsters is two levels above or bellow, as long as there's no one standing two levels above or bellow the respawn will stand still, that's why you're able to see monsters standing still in some areas where you can't reach their level or you are just standing two levels above these creatures. I don't know if it works the same way for respawn reset but my guessing is it does as long as you're neither on the area screen or two levels above or bellow again.