Good day, randyk,
Just to be clear here, you are correct in your conclusion that Christ will return to the earth to end the age after antichrist, that little horn, is given authority for 42 months i.e. the last 3 1/2 years of that seven year period. After that Christ will return to end the age, specifically after the 7th bowl judgment.
Now by saying "Christ can *only* come when he comes to destroy the Antichrist" I don't know if you are including the Lord's appearing to gather the church here or not. If this is the case, then you should not be interpreting these them as taking place at the same time, because they are two separate events, which take place at different times.
The Lord's appearing to gather the church has always been imminent, i.e. it can happen at any time. If you have the event of the church being gathered when the Lord returns to the earth to end the age which takes place after the antichrist finishes his 3 1/2 years, then the Lord's return cannot be imminent, because that event would have to take place first. And not only that event, but all of the seals, trumpets and bowl judgments which is God's wrath.
For example, the seals, trumpets and bowl judgments, as well as the beasts reign and all that the false prophet does, must take place before the Lord will return to end the age. Therefore, if I was on the earth during that time, I would know according to His word that the Lord would not be able to return until after the 7th bowl has been poured out. That being the case, the Lord's appearing to gather the church could not be imminent.
In addition to this, believers understand that God's wrath no longer rests upon them because Jesus already satisfied it on behalf of every believer. Many people overlook this by putting the church on the earth during the time of God's wrath. They also err in not recognizing that there is a difference between the common trials and tribulations that the Lord said believers would have because of their faith in Him vs. God's coming wrath, which is not the same. It is the latter that believers are not appointed to suffer. In defense of this, expositors say that God is going to protect the church during the time of His wrath. Yet, there is nowhere in Revelation that states this, nor is the church even mentioned during the narrative of God's wrath.
The erroneous claim that the church will be on the earth during the time of God's wrath via the seals, trumpets and bowl judgments also stems from not understanding the severity and magnitude of those plagues of wrath.
For example, at the sounding of the 5th trumpet/1st woe, an angel unlocks the Abyss letting out demonic beings that resemble locusts, which will torment the inhabitants of the earth with stings like that of a scorpion for five months. The context states that only those who have the seal of God in their forehead are protected from this plague of wrath, which excludes only the 144,000 who will have been sealed in chapter 7. Everyone else besides them will be tormented. Where is God's protection of the church here?
Likewise, when the angel sounds the 6th trumpet, a third of the inhabitants of the earth are killed and there is nothing mentioned about anyone being excluded from this.
Or when that 4th angel pours out his bowl on the sun giving it power to scorch the inhabitants of the earth, searing them with intense heat. Everyone on the earth will be exposed to that and no one is excluded.
These are just a few examples of what is going to take place and no one is exempt. Therefore, the claim that God protects the church during that time is nowhere listed in the narrative of God's wrath. It's just an assumption on their part.
But to recap, if it was true that the gathering of the church takes place at the same time when the Lord returns to the earth to end the age, then as I sit here writing this post, I would know that the Lord could not return right now, because all of those events must take place first. In that case, the example of the good man of the house who doesn't know at what time the thief is going to break in and therefore has to always watch, would not fit the scripture. In fact, I wouldn't have to watch at all. The only thing that I would have to watch for is when that 7th bowl is poured out.