The New Testament primarily addresses the condition of peoples and cultures within history rather than the destiny of individuals beyond history.
Much more than the Old Testament, the New Testament looks not only at the condition of peoples and cultures within history, but also at their condition outside of history - or what happens to people when they are faced with the consequences of their actions before a timeless God.
So for instance, it is quite a leap from noting the reference to dead bodies being thrown into the valley of Hinnom in Jeremiah, and bracketing Jesus’s references to Gehenna exclusively with the Roman siege of Jerusalem. It is also no more than assertion to say that the bodies of the unrighteous in Mark 9:48 are unconscious. If the passage simply describes what happens to corpses, why are they being perpetually consumed by worms and fire?
The context of Mark 9:48 is also important. There is no direct association here with judgement on Jerusalem, but there is universally applicable teaching on sin and its consequences. The perpetual suffering of verse 48 echoes the “unquenchable fire” of verse 43. Radical measures to deal with sin are urged in this life in the light of much greater consequences to come beyond or outside this life.
Matthew 8:11-12 describes “a place (where) there will be weeping and gnashing of teeth”, when gentiles come into the kingdom of God (figuratively described) and “the sons of the kingdom” are cast into the place of “outer darkness”. Either this is just poetry with little realistic meaning, or it refers to “a place” of realisation, outside this life, where the unrighteous “sons of the kingdom” see the full force of their exclusion from the benefits now awarded to those they themselves had strenuously attempted to exclude. There was little possibility of the unrighteous seeing these things within this life during the chaos of the war with Rome and the destruction of the temple.
In Matthew 13:47 we could argue over what precisely Matthew means by “the end of the age”, but the language takes us out of exclusively temporal events within history, with the activity of angels gathering together the unrighteous and casting them into “the fiery furnace” which is also “a place of wailing and gnashing of teeth”. Again, either this is simply poetic hyperbole, or it means that the unrighteous will become aware of their separation and exclusion from the benefits given to the righteous, and react in the ways described. This must be in some sense outside this life, as it would be impossible for the unrighteous to see the rewards of the righteous in a way which might cause this reaction in the chaotic years of the war with Rome.
Luke 6:19-31 may well be a parable of reversal of fortune of a kind which was well known to Jesus’s hearers. The striking fact is that Jesus does not try to correct any mistaken view of life beyond this life that it may contain, in describing the torment of the rich man in Hades. It is notale that Hades is used here, rather than Gehenna, which might have been a more appropriate location for suggesting punishment.
Whichever way you interpret Revelation 14:9-11, either as a past historical event, or as throughout history, or as yet to come, or all three, the fact is that verse 11 says “And the smoke of their torment goes up forever and ever, and they have no rest, day or night, these worshipers of the beast and its image, and whoever receives the mark of its name.” This could hardly be said to encourage a belief in simple destruction within history, with no future consequences.
It is also difficult to assert that whereas the beast and the false prophet will suffer perpetually in the lake of fire, Revelation 20:10, others who find their way there will not, Revelation 20:14-15, Revelation 21:8. Why suffering for some but not for others - in exactly the same place? Or to put it another way, why do we have the right to assert that the same location has one effect for some, but not for others, when the text gives no grounds for making this differentiation?
It doesn’t really matter whether you say that every reference to Gehenna, Hades and the Lake of fire in the New Testament relates only to past historical circumstances, or whether you say they refer to circumstances continuing, or yet to come. The content of the references indicates something rather different from simple annihilation through destruction.
I would think the greater emphasis of consequences to actions outside this life which we see in the NT in contrast with the OT is to do with the climactic entry of Jesus into the narrative. Jesus not only precipitated the “end of the age” for Israel and her temple. He also heralded the end of all ages. Every encounter with Jesus then and now confronts the individual with choices which will have consequences on their destiny beyond this immediate life, into the future new creation which Jesus came to prepare us for, whether you think this is a remote horizon (Andrew) or rather more pressingly presented in the NT (myself).
Jesus was not merely facilitating continuation through survival for the people of God, albeit in a different mode of life and expression from before. He was doing then what he does now: which is to invite everyone to step out of an old mode of life which is dying, into a new mode of life which lasts forever, for which a new environment beyond our present environment is being prepared.