take note in Matthew 25 that both Believers and Unbelievers have the same body substance. In I Cor 15 that substance is described as indestructible. Thus punishment or fire on an indestructible substance that can not be destroyed explains why eternal punishment has no end. In Matthew 25:46, if you change the meaning of eternal for punishment, then you will have to limit them meaning for eternal life to mean the same length. If both do not mean that eternal is without end, then why even bother becoming a Christian, since life in heaven or on earth would be too short to enjoy with God.