Why didn't Aldrich Killian use the fire-breathing in close combat against Tony Stark?

Watching the scene again, it's quite clear the fire-breathing moment was the result of a purge required after sustained use of extremis' exothermic capabilities.

After applying extreme heat through his palms (for what is inferred to be some time), Rhodes is ejected from the suit. Killian seems to struggle for a few moments in an attempt to contain the sudden halt of this process, before venting the built up energy through his projectile fire-breath.

Both Killian and Savin look somewhat shocked at this. It appears as though this has never happened before, but perhaps only because circumstances have never dictated such application.

Killian even make a remark about this, claiming it is 'new day' in reference to this development.

Given the spontaneity of the reaction, its unlikely Killian would be able or willing to try and reproduce it in a weaponized way...

Looking at the scene, it looks like the fire breath takes quite a bit of effort to do and being constantly in battle with the Iron Man obviously was draining to Aldrich. Additionally he then got blown up in the suit weakening him even more!

Let's take a few things in mind:

1. Iron Man 3 is based on Extremis comic book which features these superpowers on people who use the extremis virus. Obviously the whole scene is a reference to the comic.
2. Why ask "why didn't he", instead ask "would you" or something similar. The whole idea of someone forgetting or not being able to do something is for the most time a really big part of the movie (although not this one for sure but I hope you get my point)
3. Was there any weakness to that power he used? Was it maybe just a onetime power he could use? Was it even efficient enough to be used against Stark? Was that really fire and did it hurt him when he was using it?
4. Maybe the whole fire scene was a plot device to show how serious Killian was. Maybe it was nothing more than a MacGuffin to quickly turn him into a really bad guy who SHOULD be taken more seriously than we thought.

I remember Killian was asked what happens if you go too hot. Maybe he took a huge chance doing that and it was really close to the "too hot" point. That's why his accomplice looked so shocked that he would go to that extreme and take that chance. He definitely was glowing aloy brighter than the others usually did when using the power.