How long do you believe an intelligent and inventive
species can exist?

Well, if we're any example, then I'd say, not all that long !

We're about to poison ourselves out of existence.

You might want to read Arthur Clarke's sci-fi book
"The Fountains of Paradise",
https://en.wikipedia.org/wiki/The_Fountains_of_Paradise

It describes "starglider" on pages 74, 82, 92 to 96.
Interesting ideas.

Interesting, but realize that science "fiction" is just that.