It is my understanding that throughout Roman civilization, the flame of Vesta signified Rome's strength. For it to go out meant the republic/empire was doomed to fall, or already had.

I know the Vestal Virgins tended to the flame religiously, so my question is two-parted.

First: Did the flame ever once actually go out and what was the reaction of the populace if so?

Second: What techniques or methods did the Virgins have for maintaining a constant, albeit strong-enough flame for centuries and centuries?