Easyreader has an excellent point about an end-times cult needing a date.
Dates are what made the BORG successful for so long.
And, what made the dates believable, to those who bought into it, were the seeming scholarly examinations of the scriptures which led to the fanciful numerological contortions to make the predictions. It is a formula they have used over and over, with success. Of course, the pseudo-scholarship was accompanied by self-proclamations of having God's spirit exclusively.
The problem now is that they have painted themselves into a corner with dates that are immutable with respect to the foundations of the whole set of doctrines.
Of course, it would be foolish for us to count them out. They could always pull something creative out of their ass and feed it to the faithful who are hungry for anything that would bring Armageddon back onto the horizon.