Provided you don't recruit them, they will remain in the Friendly Arm Inn until you start Chapter 2 [entering Nashkel or the vicinity]. If you recruit them and then drop them before speaking with Berrun Ghastkill, they will likely abandon you.
After you've cleared the Nashkel Mines and reported your success, however, they most likely behave just like any other NPCs: You can boot them from the party and they will remain where they are, provided that they're satisfied with your Reputation.
__________________
Volothamp's Comeuppance
Everything you ever needed to know about the entire Baldur's Gate series......except spoilers.
|