Really, Moo? Were you not a Witness for very long, if at all? I remember questions like these intrigued me as a kid. This and questions about dinosaurs. lol.
IMHO though, the basis for concluding how long animals will live in the new system is plagued with holes.
You see, human lifespan and subsequent mortality is conveniently explained by the doctrine of sin and redemption. But how does the Bible explain the VARIED lifespans of non-human organisms?? There are trees that live for a 100 years, and there are trees that live for many thousands. There are turtles that live for several hundreds of years and there are fishes that only live 59 days! You'd think that for creatures that were COMPLETELY unaffected by Adamic sin, they'd have more standardised lifespans. After all they were all created on the same "day" and were all declared "good" weren't they? So how did they come to differ by so much?
What did the little pygmy goby fish do to Jehovah Almighty that the giant sequoia did not?
So if the Bible's record cannot account for such extremes in lifespans, why should we expect it to tell us how long they would live in the "new world"? The WTS did the Bible a great dis-service by making these assumptions.
INQ