Do they leave right away, or does it take some time?

I just want to know what happens. Here's my situation:

I'm playing a party of mixed alignments, and Edwin and Korgan are in. Just as an experiment, I talked to the guy outside of the Circus tent with a Reputation of 18 (he gives you +1 Rep after saving the tent). While my evil dudes complained at the action, they didn't leave. I had a savegame right before doing this, because I had read that Evil NPCs jet after your Rep goes higher than 18.

I decided not to push my luck, and went back to the savegame before talking to the circus guard.

As far as I can remember, evil characters leave at party reputation of 20 or 19 (I don't know what the manual or guides say, but for me, it was so).

The reputation table in the guide shows that evil characters will "break" when the reputation hits 19. At 18 they are "unhappy", but they will remain in the party.

I noticed after I installed the Virtue mod, NPCs who dieslike my current Virtue complain a lot more and more often (once every 24 hours?), but didn't leave. I had my Virtue well over 18, and VIconia and Edwin in my party were both complaining, but neither left. *shrugs*