The same thing applies here, if the in power Afghan government can not hold out against the insurgents now they will not be able to in 2014.
I know people don't like listening to history but here is what happened to them last time. The Russians finally had enough and left. After they left the in power government they left behind maintained power and in fact its military performed better than it did under Russian military help. Even after the Russians left it stayed in power until the Yelsin government quit supporting it.
The Afghans have experience with forign powers leaving, the Russians just left in the dead of winter and there is no reason we could not do the same.
We have problems at home we can't pay for (medicare) so we have no business wasting money and lives in Afghanistan.