If I'm building twice daily, this is nice because if a tester comes in on saturday, he wants to test the latest, there are now 14 builds he can pick from since you built twice daily.
I understand to most developers this isn't a problem, but I think this something modern, larger scale projects must deal with.
I personally took the habit to change that number on a regular basis when saving a new capx of my projects. Believe it or not, it's often far more than twice on a daily basis.
Don't mix the scale of projects and the renown laziness of developers <img src="smileys/smiley2.gif" border="0" align="middle" />
On a more serious note though, I think this had already been brought up, I'm not sure if it's on Ashley's todo list though.
A "build" property that would get iterated on export, maybe that's something quick that could get into a future release. But I'm not sure where/how you could display this.
This would probably be a value stored inside the .js file and would require you to keep a solid hierarchy/folder structures of your exports.
Until/if it's implemented, I strongly suggest to resort to updating the "Version" property by yourself though.