First, a small point: this American political sloganeering that's become so popular under Bush is really counter-productive and they should cut it out. Everyday politics are being turned into an endless election campaign.
More importantly, if the committee sincerely wants to solve the mess caused by invading Iraq they need to think about Iraq, and not focus so completely on what is essentially a US domestic concern - how many troops will be there for how long. The timeline of military involvement is an implementation detail and a US election issue, not a solution to the mess caused by the US invasion.
These are the sorts of things they should be discussing:
Benchmarks for rebuilding Iraqi social infrastructure:
- electricity, petrol supply, potable water
- schools, hospitals, government facilities
- roads, public transport
- public security
Benchmarks for creating stability as a state:
- constitution, federal government
- local governments
- civil society (indigenous NGOs)
- free press
Benchmarks for repairing the economy:
- oil industry
- rebuilding small business
- unemployment, poverty
Righting the wrong that was done:
- deal with the issues above
- truth and reconciliation commission (see Exit Strategy) or at least congressional hearings into wrong-doing by US government
- commitment of funds to repair what the US blew up
I'm sure the Great Big Heads on the committee could fill out this list more comprehensively than I can. The point is that these are the sorts of thing they should be talking about.
As to a military timeline, I think the probable best course is to pull out US troops in short order, but to replace them all (at the US expense) with trainers, social workers, analysts, etc - as well as police and security forces - who are Iraqi ex-pats, Arabs, from the UN, or at least from countries that did not support the invasion.
When you hear the figures of 50,000 Iraqis killed directly as a result of the invasion vs 600,000 Iraqis having died who would not have died if not for the invasion, the difference is largely all the people who have died from disease and from lack of shelter, drinkable water, electricity, medical facilities, etc. The US bombed electrical plants and water treatment facilities in 2003. They could have repaired them very quickly. However, repair would have involved local workers. The US chose to hire American contractors to rebuild the facilities, and that meant years during which Iraqis suffered. This is the sort of problem they must reverse. It's the right thing to do, and it's the only way to avoid decades of anti-western revolt in the Arab world.