I've been a DM since about 1989, and I've run two campaigns from 1st to 20+ level.
The first was an all 2E game that ran for about 3 years, from 1990 to about 1993.
The second started as a 2E game in October 1999. We played up to 10th, and planned to stop when 3E came out. The first 3E campaign was a disaster, and the players converted their 2E characters over. We converted again for 3.5, and finally retired the campaign in, I think, 2005. When we stopped, the PC's were between 19th and 21st level.