Yes-ish.
I was part of a shared world homebrew campaign lasting 25+ years in which games were played at a variety of character levels. The ones in the uppermost story levels would occasionally cameo in the others as NPCs. It started in an AD&D/2Ed amalgam, and died in 3.5Ed.
However, I have run 2 SUPERS campaigns using the same setting, with different players in different cities, and using 2 different systems. The characters from the first campaign were part of a different organization, on a different continent and whose actions preceded the latter campaign by 14 years. For the record, the first campaign was probably my pinnacle as a GM; the latter fizzled after a few months.