When does Satan come back?

Les teaches that after Christ returns, sets up His glorious kingdom, and rules for a thousand years of perfect rule with no poverty, war, or depression, a new generation is born to the believers who entered at the front end. These children have never had to make a choice. To prove the innate rebelliousness of the Adamic nature, Satan must be released. So when Satan comes back at the end of the tribulation, it is for that specific purpose: to try and test these new generations who have never made a choice. And again, they will follow Satan.