600 million years before the Earth becomes too hot to support the carbon cycle.

Safe to say humans will have problems long before that.

although even 1000 years is a very long time with our current rate of technological progress. credible plans exist to change the orbit of the Earth to keep us in the Goldilocks zone.

edit: for the doubters/downvoters.

https://lifeboat.com/ex/lets.lift.the.earth