Change Earth's albedo
...and we could last a whole lot longer. A big filter-shell. We'll need something like that to hang on to our hydrogen and nitrogen after the magnetic field packs it in c. 500 million years from now.
Of course to dodge the Red Giant stage we'd need to move Earth out just a bit to 1.15 AU, which we might do via arranging a perturbation from Mercury after we destabilise its orbit. Of course an accidental collision wouldn't be healthy...