I really hate to undervalue everyone's accomplishments but it should probably be known that the experience rate is quite high. Reaching God Level 12 should not take a week, nor a month, nor even three months. It should take way more time to level up. When 12 Sky 2 first came out it took at least 3, if not 5, kills on the lowest level monsters to reach Level 2. Nowadays, killing one monster grants enough experience to gain multiple levels. Basically, all of the players out there that have reached maximum level did not grind for the correct amount of time. Nobody killed enough monsters to reach maximum level, the only reason anybody is God Level 12 right now is because the monsters give extra experience.
