This is a question of gameplay versus realism - where do you, as the players, want me to put the balance?
On the one hand, I can put everything on a game time clock - if two threads are at the same place at one time, and one of them progresses by five game days while another only progresses one, the first thread needs to wait for the second to catch up before they can re-join.
On the other hand, I can put everything on a real time clock - "now" in game time is whenever the most recent post got posted, and if one group of folks ends up taking a week game time to get somewhere, and another group takes a day, they meet up without any problems, having somehow both departed and arrived at the same time.
Or I can aim for somewhere inbetween these two extremes.
The in-game example at the moment is Chapters I and III; Mr. Willoughby in Chapter III scryed on the events of Chapter I. Since then, about three days have gone by in Chapter III, and one day has passed in Chapter I - and it seems likely, given the time compression inherent in long distance travel by horse, that this ratio is only going to get more skewed, not less.