TL;DR the sun is expected to continue brightening, and that's likely to cause the end the carbonate-silicate cycle in a few hundred million years, which will mean the end of photosynthesis soon (for geological values of "soon") after that starts to grind to a halt. The end of photosynthesis means the end of large, complex life-forms on earth, permanently, forever, never to return.

This means that the practical end of the Earth, as far as humans are concerned, is on track not for a few billion years from now when the Sun expands—the commonly imagined end of "Earth gets charred/absorbed by the Sun"—but a few hundred million years from now. Maybe sooner for a variety of reasons, but that's likely to be the final lights-out—the upper bound—for everything but some microbes and a few lobsters around deep-sea vents or whatever. Barring some serious intervention by intelligent, technologically-advanced life, anyway.