It would be hard to lose this one, since we are basically finishing up what we started in '91 and should have finished then - we removed Saddam and made sure Iraq is not a threat to its neighbors. No, I don't believe this was about WMD, and no, I don't think we should stick around past the end of this year to try to make it a better place.
To be honest, I think our biggest concern is the radical schools in Saudi Arabia, the money that appears to be still flowing to the terrorist groups, and the fact that the Taliban/Al Q are still floating around.
No matter what we do or how long we stay, the place is another Yugoslavia. The best we can do is help the Kurds and keep the big weapons out of the hands of the Iraqis.