Dimon used to joke that his retirement was five years away, but now he's getting serious about the matter. JPMorgan Chase CEO Jamie Dimon, 69, has been running the biggest bank in the U.S. for nearly two decades. Related: JPMorgan Chase CEO Jamie Dimon Shares Four Tips for LeadersDimon became CEO of JPMorgan in 2006, after serving as the bank's chief operating officer. Photographer: Qilai Shen/Bloomberg via Getty ImagesAt Investor Day this year, attendees were examining key executives in the running to take over as CEO when Dimon retires. According to The Wall Street Journal, JPMorgan's CEO of consumer and community banking, Marianne Lake, 56, is a top contender for the CEO spot.