Conversation so far:
What was John O. Brennan nominated for?
Obama nominated John O. Brennan as his next director of the CIA on January 7, 2013.
Was John O. Brennan a popular vote among others?
No, Kentucky Senator Rand Paul began a talking Senate filibuster prior to the vote to elect John Brennan as the next CIA Director.
What were John Brennan's qualifications that made him eligible to be nominated?
John Brennan began his CIA career as an analyst and spent 25 years with the agency. He was a daily intelligence briefer for President Bill Clinton.

Question: How long did he hold this position?
Self-contained rewrite: How long did John Brennan hold this position?