I moved from the session system, the main purpose of activity hours is to see if there's good sync times, though given the short time it takes to make a post anyways I suspect a player could check the thread for a few minutes daily and make a short post.  The player whose turn it is will get a [@Mention] notification.  The most time consuming posts are collaborative scene posts (for that reason dictated scenes that you ask and have the next player answer are what I suspect will be more common).  Chances are early on the focus will be on making periods, expanding on the periods the game is starting with and events before delving into the scale of scenes.  However even collaborative scenes in theory should only take 15-30 minutes at most since the scene ends when the proposed question is answered, continuing said scene being done by asking a new question. Hell, characters introduced in one event may transfer to other events or even periods depending on the context.  

I should note that a way to prevent another person from offing a character you want alive for a certain period is to establish the point in time when said character is killed off before someone else does.

Also while suggesting ideas is not allowed, discussion of what currently exists is.  For one, it seems that the TL overview is shaping up faster than I initially thought it would.