Glenster, Nice try, but let me have a go too.
I didn't understand this until I heard an explanation.
There are two things to appreciate first:-
1 - "It is not for you to know the times or the seasons, which the Father has put in his own power" Acts 1:7. Essentially, we should always be ready for the Lord's return and the final Day of Judgement. It might come today or tomorrow, it is not for you to know, but you must always be ready whenever it comes. So I am not going to say it will not come for many years yet. If I were to tell you that then you might think to have a little holiday from holiness, and that might be fatal for you. Matthew 24:42-44.
2 - Look at Matthew 24:1-3, and you will see that the disciples make an incorrect assumption which the Lord does not fully correct (because of point 1 above(?)). They assume that when He talks of the destruction of the temple he is referring to the day of his coming, and of the end of the world.
"and his disciples came to him for to shew him the buildings of the temple.
And Jesus said unto them, See ye not all these things? Verily I say unto you, There shall not be left here one stone upon another, that shall not be thrown down.
And as he sat upon the Mount of Olives [[overlooking the temple]] the disciples came unto him privately, saying, Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world?"
So the Lord starts by telling them the temple is going to be destroyed. He is referring to what happened (surely) in AD70 when the temple was destroyed by the Romans. But the disciples jump to the conclusion that he is referring to the end of the world.
In Matthew 24:34 - "this generation shall not pass till all these things be fulfilled" - he is perhaps telling them:-
1 - merely about what he was originally talking about, and what started the whole conversation in the first place: the destruction of the temple.
2 - But possibly, he is referring to more, he is saying the beginnings of the end times, with all the persecution, and the spread of the gospel worldwide, start around about the time of the destruction of the temple. This generation will witness the beginnings of the endtimes with the new way that God shall be working, not just amongst the Jewish people, but amongst all the peoples of the world. Indeed, the gospel did have great success in the early church, and the gospel was preached across the whole known world in short time, so we might say the gospel was preached in all the world before that generation passed: it witnessed a great work of God. Also, the great persecutions of Nero and others had already started, before the destruction of the temple.
But note, there is much that shall happen before the day of his return, and he said so. This generation shall witness at least the beginnings of the endtimes, but I shall not tell you exactly the day of my return.... it won't help you and it doesn't belong to you to know .... be always ready.