Well, if you check from the completion stage of one quest, you only need to check the other three, surely?
On the grounds that you'd not be checking if the quest wasn't completing.
Of course, this assumes you're going to spawn the new notes from the quest directly, rather than some other quest that monitors all four. If you do it that way, you would indeed need references to all four.
Yeah, from the previous thread (not this one, but the one he linked), I suggested that he monitor it from a script that all four quests call, since any of the four quests could be the last to complete. To make it easy, I would just make one generic script that all four quests call (which would need to have all four quest properties defined.)
In that context, does it make sense? I don't want to steer him in the wrong direction!