The Delay in the Second Coming of Christ (gr. Parusieverzögerung) is a central problem of the Christian experience, structurally intimately related to the Delay in the First Coming of the Messiah in Judaism.
In the case of the Christian expectation, the Messianic Age shifts into the Apostolic Age after the Ascendency, with a preservation of the charismata and the pre-apocalyptic expectations of radical social change and focused values lived in the new communities. The ones alive now may not taste death.
In the time of these pre-apocalyptic preparations, since everything is focused on the Second Coming, there are no more long term concerns other than the salvation of the elect. If the Second Coming is a few years away, why risk the fight with the Romans and abolish slavery? Why distract oneself with marriage and children, if these can never see the fruition of their learning and intentions? Why give the lapsed a chance of redemption, if their return will not complete before the Second Coming? It is a race, and not a very long one at that, and you give your all because the prize is only moments away.
Yet just the same way, the Forces of Darkness increase their onslaught, to stem what they can, before the Final Battle of Good versus Evil, to tip the scale if they may, in the continuation of the delusion that they always were suffering under, that they had a chance to succeed against the Divine.
And then nothing happens. The first of the inner circle begin to die off. One wonders whether Joseph Smith Jr was disappointed that King Follet would not live to see Zion built, and whether that disappointment powered that funerary oration.
This simultaneously creates multiple problems. First, there is now a before and after within the waiting for the Second Coming; there are those lucky few, the pioneers, those proximate, the Apostolic, who were close to the charismata and to the Saviour himself. The very homogeneity that had been introduced as part of the social reform has now been undercut at the religious level. Paul fights to overcome this gap of not having known the earthly Jesus personally, through his powerful vision and conversion experience, but with the passage of time himself turns into one that it would have been so awesome to know. Henceforth, the majority of the people are second class citizens in the kingdom of God, living ever farther away from the Apostolic age.
Second, the radical social aspects of reform begin to run into the issues of long range planning. If no one marries, the group will die out. If the world is not about to end, it may become necessary to hold on to slavery, both in the farms and in manufacturing and in the households. The radicalism is unsustainable in the face of the need to last a few generations more, rather than flaunt consequences of the social transformations because it is only for a short time anyway.
Third, the passing of time loses the specificity of the message. The radical solution offered turns into this venerable opacity whose contribution stops making sense. The big deal regarding the sacrificial meat disappears as ritual slaughter does. As the Indian question subsides, whether they descend from the Israelites or not becomes a moot point.
Finally, the forces of evil seem to be winning out, as their stemming appears successful. And their power appears on the increase, as the worldliness washes back into everyday life and the radical social reform falters under the onslaught of the average and habitual.
The problem cannot be resolved by a repetition of the ab obo experience, by a new prophet or a new revelation, even in the face of Millennial expectations. The new exceptionalism turns into the old humdrum again, as the pattern repeats. The prophet is justified by the Millennium, and not the other way around.
But the two-class of the lucky proximate and the unlucky in-betweeners makes it clear why the idea of a repetition, of another prophet, is so appealing. It is an equalizer among the believers, reducing the class division for the present-day generation. And it fixes the creep of the changing times, for the unchanging message to be re-synchronized with the present times.