But that was my point. In the 500 or so million years of life on Earth, there have been anywhere from 5 to 20 extinction events. And we live in a very dull part of the galaxy, so most of our events are local—objects whose origins are within our solar system got us.
Yet sauce for the goose is sauce for the gander. That is, any life form will likely have to deal with such extinctions. Add to that good old fashioned natural selection, which means that a form of life either finds a “perfect niche” and stops evolving, or it evolves itself out of business, and is replaced by something better, depending on what better means for their circumstances, and it is highly unlikely that *any* form of life will be around for a billion years.
And, even though we might imagine faster than light travel, so far there has been not the slightest hint that such a thing is possible. Not at the macro or quantum scale.
And, I might add, that even if Earth screams its fool head off, anything we might do is still restricted by the speed of light. So if there are aliens out there, they have no idea that we exist.
We're like paramecia here who are referring back to our very limited understanding of the laws of physics and finally deciding that, no, there is NOTHING, NO WEAPON AT ALL, that humans could possibly have that they could use against us.
I'm not as confident as you are that creatures billions of years more advanced than us would have no way of getting to us and destroying us if they so desired.
As far as no species (on earth) ever lasting a billion years, that rule of thumb may not apply to advanced species that have engineered themselves into some highly optimized form and spread out over vast regions of space and time.