I highly recommend David Schorr's takedown of the "timelines mean they can wait us out" argument bandied about by those unable to rethink the quagmire they've aided and abetted.  As Schorr notes, the argument is irrelevant;

A lot of talk about "signals" lately. Signals to the enemy. Signals to the troops. Anyone who has read Sy Hersh's 1982 book on Kissinger, Nixon, and Vietnam, The Price of Power (out of print, unfortunately), should be extremely wary of military action as a communication medium. We should always ask whether the signal we're sending is the same one being received by the other side.

Force is sometimes necessary to achieve military, political, and strategic objectives. It can also be an effective complement to diplomacy. But in all these contexts, the connection to the desired aims must be specific and explicit, rather than general and vague. Once you adopt the demonstration of resolve as your aim, you have put yourself in a box and will have a hard time getting out.

Which brings me to the critique of a timeline for withdrawal from Iraq. If we announce one, supposedly, our adversaries can just wait us out. Okaaaay... And if we leave it open-ended, they'll do what? Insurgencies are famous for being able to sustain themselves over long periods. I think we've got something backwards here. No matter how you slice it, the longer timeframe plays to the other side's advantage, not ours. Timeline or no timeline, either way the insurgents can wait us out. After all, they live there.

That's right Virginia, they can wait us out either way because gosh darn it they live there!  

Also, I think he correctly notes that over the long haul, time is on the side of the insurgency, not us.  For example, does anybody remember talking about Hezbollah before Israel invaded Lebanon in 1982?  No, well that's because it didn't exist yet, however, it did grow out of the Israeli occupation of southern Lebanon.  Iranian support and eighteen years of guerilla warfare against the IDF and its proxy, the South Lebanon Army, transformed Hezbollah into not merely an incredibly formidable military organization but a major new player in Lebanese politics.  

I'd also like to say, be it Joe Lieberman, the White House or General Petraeus, let's stop talking about Iraq almost exclusively in terms of Al-Qaeda.  They weren't there when we invaded but they're there now and frankly they want us to stay-- or was Osama Bin Laden merely spouting off when he said his main aim was to get the United States bogged down fighting a war in a Muslim Arab country in the Middle East?  True, they have a lot of money and spectacular suicide car-bombings make a lot of news but the main insurgent groups are overwhelmingly Iraqi Sunnis .  Furthermore, much like the Shiia of southern Lebanon of the mid 80's, over the last few years these groups have become very savvy guerilla fighters.  The reason we've long associated the insurgency with Al-Qaeda is not merely the White House's political need to conflate the invasion of Iraq with 9/11 but also, if Thomas Ricks is to be believed, because that the US military has long been able to monitor Al-Qaeda electronic communications in Iraq so they tended to attribute much of what happening to a very small number of foreign fighters.  In fact, one of the more interesting passages in Rick's book Fiasco is an intelligence briefing in 2005 where for the first time President Bush is told just that, that the war is not going well and we don't know much about the organization of the Sunni insurgency because its based on blood and tribal relations we can't infilitrate and don't understand.  Nevertheless, the intelligence officer describes how millions of dollars from exiles in Syria are being hand delivered to groups in places like Ramadi on a monthly basis. 

In the long run it doesn't matter if we say we'll leave next month, next year or a decade from now; the insurgents live there, they have their own agendas, we don't know a hell of a lot about them and at this point there seems no hope of the Iraqi government and parliament reaching any sort of political solution that will bring them back into a national debate not dominated by guns and bombings. 

Update (4/27/07):  I think I meant to say "can't recommend any more highly" but neglected to put in the "any more highly."  Oh well...