I just don't follow the 600,000 number as the presumed interval between eruptions. 2,000,000 - 1,300,000 = 700,000; 1,300,00 - 640,000 = 660,000 years. This produces an average interval of 680,000 years between the last 3 eruptions. If the average is used then there's still 40,000 years before it blows. If the last interval is used then there's 20,000 years left. However, if the rate of interval decrease is applied then it should have blown 20,000 years ago (at 620,000 years).
I guess this is why we pay scientists the big bucks, so they can propose some arbitrary number and say "in the final analysis we really don't know". So we're left with prophesy, numerology, tea leaves and the Weekly World News. Maybe Bat Boy can join the USGS and figure this all out.
That's why I'm emphasing the need for caution, and precaution.
How many "smaller" blows happened before the big one?
Is it 600,000.0000?
No.
So is it 4-40-400-4000-40000 years?
For geologic events..... That IS exact!!!!!
We don't know. Exactly. We only know approximately.