What criteria do you use to determine if a passage of scripture is an allegory? The Lord is my Shepherd. I see two allegories here. Shepherd and sheep. If we see the meaning of the allegory in this passage, is it the same elsewhere?
It should spell out the allegory clearly, e.g., Galatians 4 where Paul used the images of the bondswoman/Mt Sinai and the freewoman as allegories of the two covenants; one depicting earthly Jerusalem and other the heavenly Jerusalem. Earthly Jerusalem is in bondage, while “the Jerusalem above is free, which is the mother of us all.”
Revelation 2 and 3 have no characteristics of a biblical allegory. The notion that they depict dispensations/ages within a dispensation is pure invention.