Keep in mind this was in 2006, before the first expansion pack, when it was a more balanced game from level 1 to level 60. I started playing in 2005, and it took me the better part of a year to hit 60 with my main.
There are other factors to consider as well; as someone else said, it could be about server ranking. It could also be about "completing" the end game by defeating all of the instances and dominating the arenas on his server. Considering there is no way to truly "beat" WoW, as the end game changes with every new expansion, I'd say he set a goal for himself and accomplished that goal, and was ready to move on to the next (real world) challenge. I certainly grew bored with the game after spending my second year playing the same instances over and over.
There are other factors to consider as well; as someone else said, it could be about server ranking. It could also be about "completing" the end game by defeating all of the instances and dominating the arenas on his server. Considering there is no way to truly "beat" WoW, as the end game changes with every new expansion, I'd say he set a goal for himself and accomplished that goal, and was ready to move on to the next (real world) challenge. I certainly grew bored with the game after spending my second year playing the same instances over and over.