Actually, I think that was me who was confused and not Mike and the Boys.........
I may not have been paying enough attention to this wonderful feature film, but I could have sworn the 500 year gap was between the first girl being born and the new girl becoming 20.
What I was referring to was their comments during the riff: THEY have commented at various times during various films (not just this one) about things that were explained in the narrative. [And them talking over something, then commenting on what was 'missing' was likely why you thought something had been missed by the filmmakers: you were listening to them, not the narrative.]
Don't get me wrong, the film had some serious flaws (having a plot that could have been accomplished in less time than the flashback lasted, for one). But just not some of these.
If that one agent had succeeded in killing her, the whole crisis would have ended.Yeah, but then the good serpent - who would be helpful to the universe - had to go without being a dragon for another 500 years.
And the guy did keep hoping that there was a way to help the good serpent/dragon AND keep her alive....
Good points PS-CD, that the good dragon would not be able to 'protect the universe' until whatever transfer from her 'core' happened, and the whole cycle would keep repeating every 500 years any time the girl died before it was finished (which, apparently, was the norm). So some of the plot points that the riffers riffed on as if they weren't there, they had actually just talked over the top of, and were actually covered by the voice-over. So some seemingly major 'gaps' in the plot didn't actually exist. [Others still did.]
Again, not enough to make it a good film, but like you I do think focus should be on where it actually WAS lacking.