I selected the caravan perk that makes that a merchant caravan arrives every 3-5 days but it is broken, every time a log back into the save file a caravan spawn, if I save and reload again it stacks, I can have 5 caravans at one time, I think it you can stack more but did not try, also the caravans does not leave of if they leave the leave some (if not most) of the pawns behind.