Regarding the potential third LOTB leg, I'd definitely prefer the new album and an album tour, since I've already seen the LOTB show and moving forward would just feel a bit more satisfying than dragging this tour into a third year.
But then again, there's definitely a point at bringing the show to Australia and other so far omitted markets. The rather confident statements by the band members regarding the active years (the overall impressions seems to be that they intend to go on for a couple of years anyway) might contradict with this conclusion, but just as a thought: maybe acknowledging the limited tour years they have left is actually one of the reasons why they might give LOTB a third run. As far as Maiden sets go, it's pretty appropriate selection of some of the most essential stuff, covering
all the "main eras" of the band. Sure, the most ideal Maiden history run-through would probably have one or two different songs, but there's only so much you can include within a 15 to 16 songs setlist structure.
Also, at this point, it's not like their tour legs are going to get any longer. TBOS 2016 was rather big, but it might be that the next album tour will follow the "summertime only" schedule. And - for example - since that the big markets mentioned earlier were completely left out from Maiden England schedule, it's not too far-fetched to expect the current "history/hits" tour to reach there early next year. It might very well be that it won't and they just announce the new album & album tour, but who knows.
My point being: with the limited amount of months they're currently willing to spend on the round during one calendar year, covering the whole world with one tour concept is going to take at least two years, and with the current touring model, it's pretty much three, and assuming that they're not willing to completely dismiss the markets outside NA/SA and Europe for the rest of their "active years", it might very well go down to decision whether to visit the mentioned markets with the LOTB concept
or with a new album tour -since doing both
might be out of the question.
Naturally, it's just guesswork and speculation at this point (duh) and they might very well roll out with a TBOS like world tour after the album release, but I'm just merely pointing out that they might see LOTB as a possibly last "history/hits tour" and therefore something to feel confident and safe to drag on for just a little longer. For the very reasons mentioned in this thread. Wasted years or not.