My suspicion that they would destroy the sun has more to do with their action as potential heat sinks due to their indestructibility than their drain abilities.
Sorta ties into something I thought about much earlier;
-- The easiest way to prevent LV from killing HP would be for HP to convince LV that his intention is misguided. -- His intention is to kill Harry to save the world. (funny, that) -- Killing Harry will not save the world. It is clear that LV is aware of this, based on his reflections on self-fulfilling prophecies. -- LV intends to defy the prophecy at every point of intention, and will therefore try to kill HP anyway, because if the prophecy is coming true anyway he's already screwed and has nothing to lose. -- Convincing LV that killing HP is useless is therefore insufficient. He must be convinced that killing HP will bring about the very thing he wishes to avoid. -- HP's existence must be tied to the continued well-being of the world. -- What does HP have that could save the world? Well, power over dementors. -- What might dementors do that could destroy the world? Jump into the sun, perhaps? -- The realization that that would be an optimal thing for death incarnate to do will cause the thing itself to happen. -- Unfortunately, the vow cannot prevent this, because it allowed for the weighing of risks, which by nature includes contemplation of disastrous possibilities. (if I die, does this end the earth? Is it dementors? if I don't think about this question, and they've done something, that's a certain bad thing, but if I think about it, I might decide there's nothing wrong and that's a not-certain bad thing, so I'll take the lesser risk and think about it.) -- HP is the only one who can stop them from destroying the sun. And if he dies, he cannot prevent them from doing so. -- Not that killing HP would be intelligent in any case, as there's a non-zero chance that his death and subsequent entrance into the horcrux system would kill LV too.
I'm very interested in commentary.
And that not-aging thing the regeneration ability grants her isn't necessarily going to be awesome either. What if her body decides to continuously regenerate into the form of her present-aged self?
Exactly my thought. Aaaaand there was mention of apparating one into the sun.