How long do you think the Watchtower can speak about 1914 and have followers think it relevant? I think for people born in the 1900's, it feels like an acceptable year. But what about those born since 2000, will 1914 seem like a year of relevance? Seventh Day Adventists still present years from the 1800's as of prophetic significance, so maybe it is possible to carry on such lines of reasonings for a couple of hundred years?
If someone said a year 1514 was the start of time of the end, I doubt anyone would take that as reasonable, or place any weight on comments that the end "is soon." What about the 1600's, or 1700's?
For a JW, is there a cutoff, such as 2054, where almost no follower would still be able to swallow the 1914 message? Which leads to the question, in what year will they drop 1914?