Imminency of Christ's return
Steve Hall says,
Many Christians today have accepted a "pretribulational" view of the second coming of Christ, not on the basis of careful independent Bible study, but on the basis of the perception that some of their favorite Bible teachers have accepted that viewpoint.
The verse from Matthew 24 must be taken in context. In fact, in Matthew 24 Jesus is teaching against the idea of imminency. He is reminding His disciples that before He returns, there will be the time of the great tribulation. Only one return is mentioned in Matthew 24—a posttribulational return. In verse 21, Jesus warns, "For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be." Then, in verse 29 He proceeds to relate what will happen "Immediately after the tribulation of those days." And in verse 30 He says, "And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory." This is obviously a posttribulational return. And there is no mention of any return or rapture before the tribulation given in Matthew 24. (Which is interesting in and of itself, since this is the longest discussion given by Jesus of the end times.)When Jesus warns that the church should watch for His coming "as a thief" it is in the context of being aware of the fact that His coming is near, after the events of the great tribulation! (Verse 33: So likewise ye, when ye shall see all these things, know that it is near, even at the doors.)
A close reading of Matthew 24 makes it clear that we are first to watch for the signs associated with the time of great tribulation, then expect an imminent return.
The all important Bible interpretation principle of "context" applies to Revelation 16:15 as well. As you read the book of Revelation from beginning to end, you find a description (with powerful symbolic imagery) of the great tribulation, followed by the signs in the sun, moon, and stars, followed by the time of God's wrath. God's wrath is described in the sounding of the trumpets, followed by a description in terms of the bowls of His wrath. Near the very end of all these things, just before the last bowl of wrath is described, He warns us that He is coming as a "thief."
Clearly, the warning is parallel to the warning of Matthew 24. Christians are to watch for the signs accompanied by the great tribulation, then be on the alert for our Lord's appearing.
1 Thessalonians 5:2-4
This passage contains an interesting comment in verse four. "But ye, brethren, are not in darkness, that that day should overtake you as a thief." It fits perfectly with what we have seen in Matthew 24 and Revelation 16. The day of the Lord will come as a thief in the night. But Christians who understand the signs the Lord has given us (related to the time of the great tribulation) can be prepared, so that they are not overtaken as a thief.
It is also important to consider very carefully the meaning of the phrase, "The Day of the Lord." The Day of the Lord is a very specific Biblical prophetic phrase with a definite meaning. The "Day of the Lord" does not begin until the after great tribulation has passed. You can study the Biblical details of that issue in my general paper on posttribulationalism. The point, of course, is that Christians who take the Lord's prophecies about the end times seriously will not be surprised when the Day of the Lord comes. He has left us signs so that it is not necessary "that that day should overtake you as a thief."