With all due respect, "one generation consists of 2 overlapping groups and thus can extend for 150 or more years"
FFG: In the bible story, that wt writers use to underpin this doctrine, Joseph in his generation died young, only 110 years old. Pharaoh, his fathers closer to 150. (they all were closer to wt perfection, to the talking snake timeline).
Even today, if you live in southern France, Sardinia, Okinawa, you can easily have 110 year old *** contemporaries like Joseph, and of course their timeline can span 200+ years.
The wt generation problem is not the overlap of old contemporaries. it is the anointing.
Jesus' contemporaries, as he predicted, had to die after the end of jerusalem's great tribulation. The wt generation, has to die before the great tribulation, because they are partaking in, they are causing it from heavens above.
The current wt generation is not the last.
*** old age caused by evolutionary perfecting, Healthy old men having children with younger ladies, passing on proven healthy genes.