Why is the thousand-year millennium viewed as a period of testing?
The thousand-year millennium is a period of testing because Satan is bound only until the thousand years are completed, then released to deceive the nations and test new generations born in the kingdom economy. It follows six prior periods of testing and serves as the seventh, reflecting God's pattern of completing things in seven.
Les explains that Satan cannot yet be sent to the Lake of Fire, which is a place of eternity, because he is not ready for eternity. He has one more opportunity at the end of the thousand years. God confines Satan in the bottomless pit and seals him so he cannot deceive the nations until the thousand years are fulfilled. After that, Satan must be loosed for a little season to test the new generations that come on the scene in that kingdom economy. Therefore, the millennium becomes another period of testing. Les notes there have already been six periods of testing throughout human history, and this one has to be the seventh, because God always does things in seven.