Well, I certainly was not referencing true believers when I talked about eternal punishment because the sins are against an eternal God. These would be those that are not covered by the blood of Christ. I thought everyone understood that point. Jesus Christ's Sacrifice is eternal because He is both fully God and fully man and His sacrifice will eternally cover the Saints sins.
Jer 19:5 and have built the high places of Baal, to burn their sons in the fire for burnt-offerings unto Baal; which I commanded not, nor spoke it, neither came it into my mind:
As far as this verse is concerned, this does not teach that God will not use fire in the final judgement. It simply states that the Lord never gave them a commandment to sacrifice their children - nor had He ever spoke such a thing - nor thought of such.
However, what about these, which are more to the point:
Isa_33:14 The sinners in Zion are afraid; trembling hath seized the godless ones: Who among us can dwell with the devouring fire? who among us can dwell with everlasting burnings?
In this verse, the fire and burning of God, represent His Anger and Wrath (fire), and everlasting indignation (burning).