What are we chasing in Afganistan?

I can understand why we're fighting in Afghanistan. After all, we should never have thinned our presence there while we pounced on Iraq (another story, another time). I know we have renewed our efforts to make the United States safer by keeping Al Qaeda on it's heels. I can understand following these terrorists into Pakistan when they run. What I can't understand is that we never get a score. A tally. A statement that specifies an accomplishment. Are we closing in on a target? What constitutes a victory, large or small? What is our end game? Kill all terrorists? If so, who are they? Is Bin Laden now a spectre? Is he really in charge of anything? If we are only interested in keeping America safe and not interested in restructuring the Afghan's political system (which, fortunately, is our objective) then why not get more invasive. Maybe napalm the poppy fields. A large portion of Al Qaeda's funding comes from this drug trade. I'll admit I'm not as well versed as I should be on the situation in Afghanistan, but I blame some of it on the vague aspirations of our military forces on the ground.