I think that Guild change should have a variable cooldown:
1 week cooldown for first change.
every subsequent change increases cooldown increment on switch by one week.
2 weeks cooldown for second change, 3 weeks cooldown for third change.
Every month passed in the same guilds would reduce it by a week.
So if a player has a 3-week cooldown but stays in the same guilds for a whole month, the cooldown will only be 2 weeks in the next switch. If he stays for 2 whole months instead, the next switch will have teh base cooldown (1 week).
Guild hopping IMO is a deviation of the game's mechanics and contrary to the spirit of guilds, which is to make people befriend and cooperate more with each other, making teams.
