Today we live in the Church Age, but that age does not continue forever. His Prophecy, when fulfilled, is fulfilled quite literally.
Nobody loses anything by our Lord sitting on the throne for the Millennium, but many who reject the literal interpretation succumb to an inadequate eschatology regarding the angelic conflict and human history.
"..St. Augustine ..... explained the millennium allegorically and applied it to the Church of Christ on earth. With the foundation of the Church the millennium began. The first resurrection is the spiritual resurrection of the soul from sin (De Civ. Dei Lib. XX). Thus the number 1,000 is to be taken indefinitely. ..."