Single post in Missed Event Replay

How long will the extension be for? What window of opportunity does the person who missed the event have to purchase the extension? Do they need to buy it preemptively or is there a certain amount of time after the event is over that they can buy it? (if so, how long is this amount of time?) If they didn't have enough time to do it in the first place, how will they have enough time to finish the event if they have to start over? Is every user eligible for this extension, or just those who logged in during the time it was active? Can you get a second extension for another fee?