Since the answers will inevitably contain some spoilers, I guess I should post it here...
What happens to the story/dialogue/plot progression of storyline NPCs that you have recruited but are not in your party? Do their storylines never unfold, or are there "milestones" triggered by visiting certain areas and/or doing certain things that, even if the relevant storyline NPC is not in your party at the time, you can still open up subsequent storyline dialogue with them after?
So for example, if I explore the Endless Depths without Kana and just leave him at Caed Nua.
If not, then what are the various points during the game when I should swap specific NPCs into the party to trigger their questlines?
Thanks.