I mean, it's not as if 72 years wasn't significant. As Manly P. Hall says about precession:
Each year the sun passes entirely around the zodiac and returns to the point from which it started—the vernal equinox—and each year it falls little behind the spot in the zodiacal sign where it crossed the previous year. Each sign of the zodiac consists of thirty degrees, and as the sun loses about one degree every seventy two years, it regresses through one entire constellation (or sign) in approximately 2,160 years, and through the entire zodiac in about ] 25,920 years. (Authorities disagree concerning these figures.) This retrograde motion is called the precession of the equinoxes. This means that in the course of about 25,920 years, which constitute one Great Solar or Platonic Year, each one of the twelve constellations occupies a position at the vernal equinox for nearly 2,160 years, then gives place to the previous sign.
(Hall, The Secret Teachings of the Ages)
I like how 1260 is 2160 with a couple digits transposed, and it's 900 off. That's interesting.
Of course, what I'm getting at here is that the book of Revelation is loaded with astrology. The book of Revelation is where you get 1260 years. The WTS, of course, demonizes astrology, so their doctrine of history is at the very least internally inconsistent.
So basically, even while they discredit things like Ptolemy's Canon, etc., you could apply the very same logic to them.