Well, urm, my campaign is nearing 20 years (Jan 08 it started). The current PBEM is going on since April '04. The last new character added over a year ago. However, within the campaign context there have been at least a dozen different game settings with groups of PCs. The longest running group - roughly from 88 to 01 or so, got the highest PCs to 14th (none were there in 88 though). Some of those PCs are still active, at a Meta level, in their 20s in the current PBEM (which has a war as the backdrop).
Ciao,
Old Man