Sometimes it's best to have something to make you look intimidating, be it a large staff or a gun.
It might actually be completely useless (such as an unloaded gun or even a toy gun).
In other words, if a target hasn't had a stun effect active on them for more than 15 seconds, the next stun will have full effect.
Some abilities share diminishing returns—that is, it doesn't matter which one you use; the next time you use an ability in the same category on the same target, its duration will be diminished just as if you had used the exact same ability. It should be noted that the server does not reset diminishing returns after exactly 15 seconds.
So on those encounters, you should apply Demoralizing Shout and Screech, to fully debuff the target's AP.