As Annie, I personally don't have my stun up in teamfights...
Usually leave at 3-4 charges. If tank rushes into my team, I can q and in some cases w as well him without wasting my stun. Opponents stack, R stun them.
If they just all appear at once, E then quickcast q R w works well anyway, and lets q recharge faster.
Also, not having your stun up apparent when preparing to teamfight is useful if a single enemy charges you and you need to damage him while still wanting to stun multiple ppl with your tibbers. And avoids ppl flashing away if they see your stun up when you go up to them.