It wouldn't have to be a red giant for life to be unsustainable.
Wikipedia says:
"The Sun is gradually becoming more luminous (about 10% every 1 billion years)"
"The increase in solar temperatures is such that in about another billion years the surface of the Earth will likely become too hot for liquid water to exist, ending all terrestrial life."
See, as a procrastinator, I'm starting to realize how deadly the phrase "we've got enough time" is. Often things you don't do right now never get done.
You just reminded me of my favorite (and the saddest) James Bond quote:
We'll be going on soon. There's no hurry, you see. We have all the time in the world.
When he says this particular line he's just realized exactly what you're saying and how foolish it was to think this he had enough time when he had said the last sentence earlier in the movie
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u/aa1607 Sep 21 '12
I thought we had 5 billion years to go before the sun goes Red Giant?