The debate between premillennialism and amillennialism is not about whether the 1,000 years mentioned in Revelation 20 refers to a literal 1,000 years. Both positions agree with each other that it denotes at least a period of time. How long is not the issue.
To be sure, I do believe that the reference to 1,000 years is literal. But it is possible that it symbolizes 10,000 years or even longer, or maybe shorter. In any case, it does not affect the premise of premillennialism, which asserts that the binding of Satan occurs at Christ’s second coming, not his first coming.
Accordingly, the debate hinges on the question of the terminus a quo (earliest starting point) of the binding of Satan depicted in Revelation 20:2-3:
(2) And he seized the dragon, that ancient serpent, who is the devil and Satan, and bound him for a thousand years, (3) and threw him into the pit, and shut it and sealed it over him, so that he might not deceive the nations any longer, until the thousand years were ended. After that he must be released for a little while. (Rev 20:2–3 ESV)
Did the binding occur at Christ’s first coming or will it occur at his second coming?
All other arguments aside, there is one particular argument that strongly demonstrates that the binding will occur at the second coming. Revelation 12:9 reads:
And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him. (Rev 12:9 ESV)
Amillennialists agree that this is a problematic passage. The salient question is: How can Satan be bound in any meaningful sense of the term when he is shown in Revelation 12:9 to be thrown down to earth as the deceiver of the whole world?
And yet Revelation 20:3 gives the purpose for his binding: “so that he might not deceive the nations any longer, until the thousand years were ended.”
So is he bound at this time “so not to deceive the nations”? Or is he free at this time as “the deceiver of the whole world”? Ammillennialists cannot have it both ways, which would reveal a weakness in their eschatology.