How can heaven and hell possibly co-exist everlastingly (asks Philip Edgecumbe Hughes)?  Would this not be incompatible with the redemption achieved by Christ?  For,

• Christ “has appeared once for all at the end of the ages to put away sin by the sacrifice of himself” (Heb 9:26; 1 John 3:5);
• through his appearing death has been abolished (2 Tim 1:10);
• in the new heaven and the new earth, that is, in the whole realm of the renewed order of creation, there will be no more weeping or suffering, “and death shall be no more” (Rev 21:4).

The concept of endless torment stands in contradiction to this teaching:-

‘It leaves a part of creation which, unrenewed, everlastingly exists in alienation from the new heaven and the new earth. It means that suffering and death will never be totally abolished from the scene.’

The logic of this position was accepted ‘with shocking candour’ by Augustine:-

“after the resurrection, however, when the final, universal judgment has been completed, there shall be two kingdoms, each with its own distinct boundaries, the one Christ’s, the other the devil’s; the one consisting of the good, the other of the bad.”

But the scriptural prospect of the restoration of all things (Acts 3:21; Col 1:20) leaves no place for a second kingdom of death.  Where light fills everything, ‘night shall be no more’ (Rev 22:5).  When Christ ‘fills all things in every way’ (Eph 1:23), and God is ‘everything to everyone’ (1 Cor 15:28), no room remains for a section of creation that contradicts this completeness.  Rather, argues Hughes, ‘the establishment of God’s everlasting kingdom of peace and righteousness will see the setting free of the whole created order from its bondage to decay as it participates in the glorious liberty of the children of God (Rom 8: 21).’

In Christopher M. Date, Gregory G. Stump, Joshua W. Anderson. Rethinking Hell: Readings in Evangelical Conditionalism (p. 195). Cascade Books, an Imprint of Wipf and Stock Publishers. Kindle Edition.

John Stott argues similarly:-

‘The eternal existence of the impenitent in hell would be hard to reconcile with the promises of God’s final victory over evil, or with the apparently universalistic texts which speak of Christ drawing all men to himself (John 12: 32), and of God uniting all things under Christ’s headship (Eph 1: 10), reconciling all things to himself through Christ (Col 1: 20), and bringing every knee to bow to Christ and every tongue to confess his lordship (Phil 2: 10– 11), so that in the end God will be “all in all” or “everything to everybody” (1   Cor 15: 28).

In Christopher M. Date, Gregory G. Stump, Joshua W. Anderson. Rethinking Hell: Readings in Evangelical Conditionalism (p. 54). Cascade Books, an Imprint of Wipf and Stock Publishers. Kindle Edition.