Alright, to curtail any comments about not reading Splitinfinity's FAQ, I have looked at it and it doesn't have the specific problem I think I just hit. I understand that Ktjn has a new question for you after certain checkpoints in the game. The problem I have come across is, I didn't talk to Ktjn between escaping Bhujerba and getting the Dawn Shard. So at present I only have two of the four questions she asked answered, when I should have 3 answered, it being after Leviathon was destroyed. Have I screwed up?
there are a lot checkpoints (about twice as much than necessary) after that it's about time intervals. So no matter when you start you will be able to finish (though if you miss all checkpoints and do this as final sidequest you'll have to wait a lot.
true you can buy better stuff. But the sidequest takes virtually no time at all. it's only a tiny bit of text scrolling and choosing an answer. so it isn't exactly a side quest that should be very rewarding.