There is actually a jehovah's witness on this site you can ask, name escapes me at the moment. Typically if you ask them a question they can't answer they smile politely, say they'll do research, then return with a magazine or book printed by the watchtower and tract society (the head of their religion) that vaguely discusses your question, and then repeat whatever the book or magazine says, and if you persist then they just don't come back because your heart condition isn't right (it requires great humility to accept the teaching of god).
While they've predicted the "end" a few times and been wrong (not 10 times, though but a few times), they either say "oops" and/or readjust their thinking on the matter, re-intepret the scriptures, and move on. They've wised up though and stopped predicting an actual date or concrete timeline and just say that it is just around the corner, almost here, any day now the great tribulation will start and then armageddon, not yet, but almost. That way it can perpetually keep them waiting without ever disappointing. Much smarter than picking an actual date or saying now is the time.