It is always good advice on a personal level to put a date on your goals, but in politics however, this advice is poisonous. The Obama administration plans to leave Afghanistan while handing security duties to the Afghanistan National Security Forces (ANSF) looks to be failing to the point where the Department of defense has conspicuously tampered with the evaluation tools used to assess the progress of Afghan security forces.
According to a report by the GAO, the DOD changed the highest level of capability of afghan forces from 'independent' (meaning the ANSF can carry out a given mission "without the assistance of coalition forces" ) to 'independent with advisors' (meaning that the ANSF could execute a mission successfully but required the support of the Coalition forces.
This gave the false impression that the capability of the ANSF was increasing, however the progress was sluggish at best as only "7 percent of army units and 9 percent of police units" had reached 'full' capability. Another Problem cited in the report is the fact that the Afghan government, at least without donors, cannot sustain the army proposed by the United states and other NATO members.
There are major skill gaps within the ANSF, which contributes to the reliance on coalition forces for support as the grim truth is that the best fighters are probably with the Taliban or local warlords. the United States plans for exit are also hampered by age old problems of poor or weak governance and corruption as the government departments that oversee the military and the police either lack the 'expertise' or the will required.
In sum, Afghanistan is the longest war the United Sates has ever been involved in and unless it wants another decade of Afghani hospitality, It must address the ever pressing problems going forward.
Read the GAO report on Afghanistan here: http://www.gao.gov/assets/600/592913.pdf