Why is the millennial period the seventh period of testing?
The millennial period is the seventh period of testing because six prior periods of testing have already occurred throughout human history, and God always does things in seven. Thus a seventh period is necessary to test the human race, with Satan released afterward to test new generations.
Les explains that Satan is confined in the bottomless pit for the thousand-year millennial period, not the Lake of Fire, because he has one more opportunity at the end of the thousand years. He will be released and have full freedom to deceive the nations once again. Scripture says he is locked up until the thousand years are fulfilled, then loosed for a little season to test the new generations that come on the scene in that kingdom economy. Thus the millennium becomes another period of testing. Since there have already been six periods of testing throughout human history, this one must be the seventh, and God always does things in seven, so a seventh period of testing the human race is required.