The Taliban are growing stronger in Afghanistan. This is not a good thing. But, this doesn't mean that in order to "win" in Afghanistan that the Taliban must be utterly defeated.
A key complicating factor in the Afghanistan counterinsurgency is that to an even greater degree than in Iraq, we are there in a strictly supporting role to a weak civilian government. So, we can't call all the shots in the way that a genuine occupying army can, despite being treated like an occupying army by insurgents. The upside of this, however, is that unlike an army fighting a traditional counterinsurgency, our primary objective is not the "defeat" the insurgents.
We went to war with the Taliban, simply because they were using their position of power in the country to aid and abet al-Queda by failing to take sufficient action to stop al-Queda. Almost everyone in the world agreed that they were doing a really horrible job of running their country, but that isn't why we went to war with them.
Terrorists and the Taliban are not the same -- the Taliban didn't make any serious effort to pick a fight with the U.S., but they were unable and unwilling to get out of the way fast enough to let a 9-11 enranged world secure vengence against their allies. As long as a government in Afghanistan prevents the country from being desirable as a permanent terrorist planning and training base, it is really none of our business what kind of government ends up in power in Afghanistan.
If Afghanistan doesn't degenerate into anarchy again, creating a terrorist training camp safe zone, and so long as U.S. troops are free to take action against terrorist groups in the area, it really doesn't matter to us if the Taliban insurgency continues for another 30 months or another 30 years. As backward as the Taliban were, they weren't our primary enemy, and now that they are out of power, they are simply an inconvenience that is making it harder for us to leave. Our goal with respect to the Taliban was to deny them the ability to protect terrorists and this mission was accomplished five years ago.
As long as the current regime remains is in good enough shape to continue to deny the Taliban the ability to rule the country, we don't have to "win" the fight against the Taliban, we only have to win the war against the terrorists. When the current regime is strong enough to stay in power on its own, without being propped up militarily, we can leave.
The apparent consensus from intelligence sources, as the media and politicians report it anyway, is that the terrorists long ago fled Afghanistan in favor of tribal areas of Pakistan not under full central government control, and other anarchy ridden parts of the planet. We've mostly won the war against the real terrorist in Afghanistan and are now simply in the business of having some government in place there that is secure enough to keep them from coming back.