The Devil's "Dash"
Revelation 12:12 (NIV) Therefore rejoice, you heavens and you who dwell in them! But woe to the earth and the sea, because the devil has gone down to you! He is filled with fury, because he knows that his time is short.” (emphasis added)
On the timeline of eternity, the devil (and his reign) is just a small "dash."
Think about it... because of God's wonderful grace and Jesus's death and resurrection, we (as believers) will reign with Him forever and ever in heaven. The devil however, will be defeated (Rev 20:10.) As long as he has created chaos on earth, when compared to eternity... it's a milli-second, a passing thought.
Can you picture it? 1 trillion years from now sitting at the banquet table talking... oh yeah, the devil, who was that again?