Christ's Reign and the Last Harvest

The Tribulation is past, and Satan has been cast into hell for a thousand-year sentence, as prophesied in the Bible. Christ, in His resurrected body, rules from Jerusalem over the resurrected of the ages and the mortal survivors of the Tribulation. The people of the earth begin a thousand-year victory celebration, delighting in what should have been from the beginning, on a regenerated Earth.
Mortal lifespans are increased-humanity has no fear of savage animals, crime, disease, starvation. The Spirit of God courses through every mind. Children are born to the mortals, and the earth is repopulated.

But these new generations, free of Satan, still have free will. They still feel the temptations of the flesh and of the world to beguile, bend, break their relationship with their Father, and the Holy Book warns of Satan's final return, the last gathering of his people, and war upon the earth.
How will good people of free will protect their faith against the unknown strategies and wiles of an enraged Satan? Can rebellious mortal minds be turned back to God before Satan is freed to make his last stand?

Who will be among Christ's last harvest?