I like an open ended ending with the option for returning to these characters. So not every single thing is tied up, but we can imagine these characters maybe going their own way to follow up their own agendas with a promise to reunite someday (or perhaps more dramatically, never see each other again! - with the meta-knowledge that someday the world may call on them again despite their enmity!
)
I ended my Ghosts of Saltmarsh campaign right after they completed the Final Enemy (3 years in real time), but we plan/hope to return to these character after a year's time has passed (in-game) and in the meantime started a new campaign somewhere else in the setting which may take several years.
I ended my Out of the Frying Pan campaign after five years with characters going their separate ways after the central concern had been resolved, following after the hooks that were never pursued in the midst of the campaign. For that game we actually had a pair of reunion sessions involving hunting a dragon about a year later.