CMOs are under tremendous pressure to deliver, and the challenge is proving difficult to face. According to The Wall Street Journal, average CMO tenure is currently just 42 months - down a full six months over the last two years. In the UK, the average tenure of CMOs is only 18 months. It's by far the shortest in the C-suite: CEOs average 7.2 years, for example, and CFOs 5.7 years.