Where is the 250 million years come from?
Wikipedia's "Timeline of the Far Future" lists several:
<https://en.wikipedia.org/wiki/Timeline_of_the_far_future>
We likely exist in the late afternoon if not evening of Earth's habitable period.
https://en.wikipedia.org/wiki/Pangaea_Proxima
Life might very well exist on earth even through those conditions, but not to the extent we have today.