All planets within that orbit level, including the Earth, are doomed, and therefore have a time limit upon them.
All life on those doomed planets is in jeopardy in the very long run:
Earth's fate is precarious. As a red giant, the Sun will have a maximum radius beyond the Earth's current orbit, 1 AU (1.5×1011 m), 250 times the present radius of the Sun. However, by the time it is an asymptotic giant branch star, the Sun will have lost roughly 30% of its present mass due to a stellar wind, so the orbits of the planets will move outward. If it were only for this, Earth would probably be spared, but new research suggests that Earth will be swallowed by the Sun owing to tidal interactions. Even if Earth would escape incineration in the Sun, still all its water will be boiled away and most of its atmosphere would escape into space.(Wikipedia, Astronomy Today, PBS, and Space Dot Com). Exactly when this will happen, or could happen has become more foggy as we observe some stars going through that phase much earlier than the current stellar models allow for that to happen.
The logical behavior and path for the human species, since we are faced with this reality, is to preserve the life sustaining essence of this planet earth while we find another habitable planet within our reach. We have no reach yet (see Tenet 3(b) Basics).
Meanwhile, we must develop a way to travel to that habitable planet so we can colonize it so as to perpetuate the human species.
Tenet One is part of The Tenets of Ecocosmology which this blog focuses exclusively on.
A recent study of the Sun, which raised eyebrows, underscores our need for more study and research so as to build a more solid foundation for solar science.