Hillary Rodham Clinton announced... she is joining with Democratic Sen. Robert Byrd to introduce legislation to make October 11, 2007 -- the five year anniversary of the original resolution...-- an "expiration date" for that resolution.
Say what you will about her politics and whether she would be a good nominee, but this seems a much more likely to succeed approach than the time-tables attached to the funding bills. Bush sought authorization for the war, so it seems reasonable that the branch of government which issued such authorization could revoke it as well, no?