What has been said is very true and I agree with it. If Armageddon was imminent there would be much better ways of warning about it.
It's not necessarily true that the way a sect sustains itself has been designed by anyone. Sometimes you just have to hit on a design which works. Jehovah's Witnesses are old enough that even the people at the top are true believers, whatever you think of Rutherford et al. They seem to fill a niche - they have made converts and the high commitment and inward looking cultishness has been successful in keeping members. (High commitment? Yes, this makes it an important part of your life and makes you justify to yourself you have spent your time.) This is at the expense of a huge amount of members' time, of course.