How long will it take for a JW to see that even the overlapping generation is wrong?
Having spoken to JW's that turn up their own cognitive dissonance, this is what I see:
Most still believe the end will come within their lifetime. Despite all previous claims failing, they see the organization and the GB as simply wanting to see it as bad as every other member.
Older JW's are starting to see the problem with their belief, but they decide they have too much time invested and will just have to hope they were right. Younger JW's can and will wake up, but the ones who don't are so all-fired sure of Armageddon within 10, 15, 20 years- whatever works in their mind.
The longer the time passes, the more JW's will have a problem with overlapping generation. But their main adherents will stay loyal and wait. New people won't really come in, even the kids will not keep falling for this stuff as they figure it out. But this will be a slow decay of the organization as members die off.
Meanwhile, using "this generation will not pass away until all these things occur" they can still tinker with what "pass away" means or declare that "all these things" did occur invisibly or even some new odd things we haven't thought of. But I also believe that, due to lousy recruitment, they will try to declare 2034 as something special.