So you think my character's live time in game is what? Maybe a year? Two years? If I play the same character for say 300 hours, how long would you think that character's game life would have been?
I very much think one person could run three guilds at the same time, just as I think Donald Trump has done pretty well running numerous organizations and charities all at the same time.
But really, it's no problem we don't see this the same way. We all have different ideas of what we want. I am just of the belief that having skill requirements as well as having to complete quests to be head of a guild would mean our character accomplished just that and would deserve to head whatever he/she put the time into accomplishing. In fact I think it would be awesome if it were included that when becoming a member of a second or third guild you would have to work out some issues between the guild and "build bridges of understanding" between the different guilds. Stick out the olive branch and have them work together to accomplish something huge in the game.
Some people and hopefully some characters would thrive with added diversity.