The end is coming sooner than expected, in cosmological terms. So you very far-vision SF writers may have to trim your numbers, and you SF readers may chuckle inwardly at naive writers who haven't gotten the word, yet: the sun may be too luminous to support life in a mere half to a billion years. And to add insult to injury, neither the earth nor the sun are ideal for supporting life. Well!

Here's the story in Space Fellowship.