Actually studies have shown by the time all of this has happened most Black Holes will have collapsed into there (So to say) polar opposites, white holes creating the destruction of both.

I probably over-simplified in saying that the energy would be "used up." What will happen is that the universe will reach a state of maximum entropy. All available energy will have moved to regions of less energy. Once this has happened, no more work can be extracted from the universe. Heat energy, for instance, will…