According to the LA Times, Hoover convened a meeting (that included a DoJ official) to craft an "exit strategy" from the operation. The Times says that the consensus of the attendees, including the DoJ official, was that Fast and Furious should continue until they could get indictments to show that the operation was productive.
The article says that Hoover laid out 30, 60 and 90 day windows to shut it down. That was from March of 2010. The first indictments were handed down ten months later.
It would appear to me that Hoover was unable to shut down Fast and Furious because somebody above him in "Justice" would not allow it.
http://articles.latimes.com/2011/aug...-guns-20110811