If it were possible to access all of the Earth's stored geothermal energy, probably a very, very, very long time.

But if we're open to applying a quantitative timescale threshold to the thought experiment, at which we can argue geothermal is renewable, that raises the question for nuclear. If we could access all fissile uranium and thorium on Earth, how long would it take for us to deplete its stored energy? Does that mean nuclear energy is renewable?