Is it better to try to reveal a Traitor early, or wait until later in the game?
My experience is that a known but unrevealed traitor is less damaging than a revealed traitor. Moreover, an unrevealed traitor who doesn't know for certain he's been ID'd may be of some minor benefit, especially if the solo-quests are not his to lose.

An unrevealed traitor, however, can truly sabotage the single-time solo quests something fierce... 

If the game is close to 12 swords, say 9+, and a quest is close it's time to gank the traitor to prevent 2 swords from flipping.