As time marches on, the WTBTS finds themselves in the position of needing to go to their vaults and pull out "shelved ideas", to quote David Splane. As each former idea proves incorrect ( or correct/incorrect/correct/incorrect, as in the case of flip-flops) it must be a bit frustrating for the GB and their Writing Dept. Can you even imagine being wrong almost every single time you say something?
That's one thing I don't get about the overlapping generation idea, they do realize that this will also have to be changed again at some point? Why not redefine generation as the general group of anointed on earth? As long as anointed ones still exist (and that number is actually rising) they could still say the interpretation is correct. Instead they come up with another explanation with a sell by date. Don't they learn their lesson?