When does Christ return to establish His kingdom?

Les explains that at this point in Romans he is getting ready for the return of Christ to set up His kingdom at the end of the tribulation. Revelation specifies it will be a thousand years. Yet Old Testament kingdom prophecies use terms like forever and eternally, so this thousand-year kingdom is an introduction to the eternal state. It will be interrupted, and there will be a new heaven and new earth, but eternity will still be based on the physical attributes of Christ's thousand-year reign. During the thousand years, flesh-and-blood people will have children, whereas in the eternal state that likely will not continue.