3 - The Mafia (9 months) The Brigade (2 weeks) The Immortals (ongoing, currently 10 months to the day)
Like others, I don;t think there is a specific number that constitutes as 'too many'. I think a better indicator is avg time in an alliance. if someone is 5 months old and in 5 alliances, then yea, that's a lot. but if they are 3 years old, that's a different story.