Leveling speed in Dungeons & Dragons

In any level-based roleplaying game the people who run the game need to think about how fast they want the players to gain levels. There is clearly an optimum somewhere in the middle: Too fast and players get new abilities before they had time to try out the previous ones they got; too slow and players have the feeling their characters are stagnating. So while preparing my first D&D 4E campaign, I had to think about this.My introductory adventure from level 0 to level 1 took just 2 play sessions

World of Warkraft...