There are many pre-millennials that believe that just as there are many that believe it’s after a thousand year reign.
How are you coming to this conclusion? Where are you getting that idea from? I do not believe that there are many premils who believe the following will occur when Christ returns:
Revelation 21:1 Then I saw “a new heaven and a new earth,” for the first heaven and the first earth had passed away, and there was no longer any sea. 2 I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband. 3 And I heard a loud voice from the throne saying, “Look! God’s dwelling place is now among the people, and he will dwell with them. They will be his people, and God himself will be with them and be their God. 4 ‘He will wipe every tear from their eyes. There will be no more death’ or mourning or crying or pain, for the old order of things has passed away.”
I believe a vast majority of premils believe that this will occur 1,000+ years after Christ returns. And it's not hard to see why. Once the New Jerusalem comes down from heaven then "There will be no more death’ or mourning or crying or pain", yet the Premil view demands that there will be more death, mourning, crying and pain after He returns. So, I can't even fathom why any Premil would believe that the New Jerusalem will come down when Christ returns.