When Is It Time...To Ash Out?

I'm not a smoker - in fact, since I was little, I've been told I am somewhat allergic to smoke. My Dad use to smoke a pipe and every year, around winter, without fail, I would get strep throat or some coughing illness from all the smoke that was inhaled. Finally my Dad quit, for my health, cold turkey.
Now with DC and other big cities banning indoor smoking in bars, I have to say, it's nice to be able to go out and not worry about going home at the end of the night smelling like an ash tray.

But a question I have out there for the smokers - when is it time to ash or ash out your cigarette?
The reason why I ask is because I was driving alongside this woman last night, in rush hour traffic...we were side-by-side for awhile since we weren't moving very fast, but she had her window down and she was smoking a cigarette. When I first took notice of her (I actually had to turn the air flow into internal air flow cause I could smell her smoke), she had a good bit of ash on the tip of her cigarette. As we kept driving, that ash margin got bigger and bigger - to the point that when I left her, it started to curve. I kept wondering when she was going to ash out her cigarette - I was actually worried that if she didn't soon, the ashes might fall into her car. I also wondered if it's happened to her before.

Well - I hope she eventually ashed without getting any in her car. Because if she kept going the way she was going, she was going to look like she was puffing on a candy cane soon!