Much like the previous day's question, this is something I have never done. All of the D&D campaigns I played in were low to medium level. I think this is what most of my fellow gamers enjoyed playing and running and therefore we weren't in any hurry to "get to the top".
The highest level character I ever played was also my first, Serafis the fighter. The campaign lasted almost two years in real time, and I think he finished up somewhere around 10th level in an AD&D game.