I would say that the kingdom here (Luke 21:31) refers to the end… and that the nearness can be understood in this way: when someone gets very sick or is badly injured and then recovers, that person may say that they were “near” to death. The reality is that, in surviving, they are nearer now –temporally speaking – than they were then. Similarly, Jesus’ words can be understood to mean that the destruction of Jerusalem brought those who experienced it to an experience of judgment that is “near” or approximate in degree to what will be endured by all of us when we witness the final judgment and see the destruction of God’s enemies. And so the nearness of the kingdom in this verse could be understood as referring to the “nearness” or similarity of experience.
That said, there is also an element of timing being discussed in these verses, and that would be the real thrust of Jesus’ words. But I would say that the timing aspect has to do with the implication found in the “sign” of the destruction of the temple, and not with the destruction of the temple itself. In other words, the destruction of the temple is a picture of the final display of God’s wrath against all ungodliness. And so the kingdom did not come soon after the destruction of the temple because the kingdom will come soon after that which the destruction of the temple points to – i.e., the final judgment – comes to pass.
I would take Paul’s words in 1 Corinthians as referring to individual believers. Our time is always very short. “For”, as James says, “you are a mist that appears for a little time and then vanishes” (4:14). With every passing day, we can say with Paul, “salvation is nearer to us now than when we first believed” (Rom. 13:11). So when Paul refers to the “appointed time” in 1 Cor. 7:29, I take it to mean the day of my - or anybody’s - death. And his words following where he says, “the present form of this world is passing away” (1 Cor. 7:31), I would take as a statement of fact pertaining to the nature of this world, not as a statement about how soon it is until the end of the world takes place. And this agrees with John where he tells us not to love the things in the world and writes, “the world is passing away along with its desires, but whoever does the will of God abides forever” (1 John 2:17). Not that it will happen very soon, but that the things of this world are of a transient nature.
Paul writes in 1 Thessalonians that “we who are alive, who are left until the coming of the Lord…” (4:15). I would take this as referring to
how things will take place when the Lord comes, but not as a statement referring to
when the Lord will come. Otherwise, one would have to conclude that Paul knew for a certainty that he would still be alive when Christ returned, because he said “we” which always includes “me.”

But Paul, as with all believers in the Lord, does not know when Jesus will return. This is made clear by his discussion about his own death in Philippians chapter 1: “Yet which I shall choose I cannot tell” (v. 22). So I would take the “we” as referring to those Christians who are alive when Jesus returns, whenever that may be, which does not necessarily include any of the Christians that this letter was addressed to, although it could have. As the previous poster mentioned, Jesus will return like “a thief in the night” (1 Thess. 5:2), and no one knows the day or the hour (cf. Mark 13:32). So let us make the “best use of the time, because the days are evil” (Eph. 5:16) and “Stay awake” (Mark 13:32; 1 Thess. 5:6).
What do you think? As Augustine once wrote to Jerome: “If you know any better way, my beloved brother [or sister], in which it can be explained, I beseech you by the Lord to favor us by communicating to us your exposition” (Letter 132).
May the Lord be with you,
Pete