Paul was initially hoping that Jesus would return in his own lifetime.
But later on realized that he would die before it happened.
This is why he was passing on his ministry to Timothy and others.

2 Timothy 3 “You then, my son, be strong in the grace that is in Christ Jesus. 2 And the things you have heard me say in the presence of many witnesses entrust to reliable people who will also be qualified to teach others.“

2 Timothy 4 “In the presence of God and of Christ Jesus, who will judge the living and the dead, and in view of his appearing and his kingdom, I give you this charge: 2 Preach the word; be prepared in season and out of season; correct, rebuke and encourage—with great patience and careful instruction. 3 For the time will come when people will not put up with sound doctrine. 6 For I am already being poured out like a drink offering, and the time for my departure is near. 7 I have fought the good fight, I have finished the race, I have kept the faith. 8 Now there is in store for me the crown of righteousness, which the Lord, the righteous Judge, will award to me on that day—and not only to me, but also to all who have longed for his appearing.” 

Paul realized that the 2nd coming would happen after he died. This is why he said that the last days were something in the future. 

2 Timothy 3 “But mark this: There WILL BE terrible times in the last days.” 

Peter initially thought that the end of all things was in his lifetime 
1 Peter 4 “7 The end of all things is near.”

Then in his 2nd epistle, he acknowledged that God could choose to delay it for 1000 years and more…because God wants more people to be saved. Peter said that scoffers WILL come in the last days—prophesying a FUTURE EVENT of apostasy and unbelief of people denying the 2nd coming. 

2 Peter 3 ” 3 Above all, you must understand that in the last days scoffers WILL come, scoffing and following their own evil desires” 

Peter also said that he would die before the 2nd coming happened and was passing on the Gospel message to the church after he died, especially the hope of the 2nd coming. 

2 Peter.1 ” 13 I think it is right to refresh your memory as long as I live in the tent of this body, 14 because I know that I will soon put it aside, as our Lord Jesus Christ has made clear to me. 15 And I will make every effort to see that after my departure you will always be able to remember these things.” 16 For we did not follow cleverly devised stories when we told you about the coming of our Lord Jesus Christ in power, but we were eyewitnesses of his majesty. 17 He received honor and glory from God the Father when the voice came to him from the Majestic Glory, saying, “This is my Son, whom I love; with him I am well pleased.” 18 We ourselves heard this voice that came from heaven when we were with him on the sacred mountain.”

Peter said that the world would be destroyed at the 2nd coming and that God was patient in saving people because there is no more salvation after the 2nd coming. 

2nd Peter 3 “8 But do not forget this one thing, dear friends: With the Lord a day is like a thousand years, and a thousand years are like a day. 9 The Lord is not slow in keeping his promise, as some understand slowness. Instead he is patient with you, not wanting anyone to perish, but everyone to come to repentance. 10 But the day of the Lord will come like a thief. The heavens will disappear with a roar; the elements will be destroyed by fire, and the earth and everything done in it will be laid bare.” 

EVERYTHING was going to be destroyed for these Gentiles living in the nations. That is why they looked forward to a NEW WORLD to come where there is no more sin..

2nd Peter 3 “11 Since everything will be destroyed in this way, what kind of people ought you to be? You ought to live holy and godly lives 12 as you look forward to the day of God and speed its coming. That day will bring about the destruction of the heavens by fire, and the elements will melt in the heat. 13 But in keeping with his promise we are looking forward to a new heaven and a new earth, where righteousness dwells.” 

Peter and Paul, who were approaching the end of their lives , BOTH acknowledged that the 2nd coming was going to happen AFTER THEY DIED, and that they were passing on their ministries to future generations.

The Apostle were the eye-witnesses of Jesus in His death, resurrection. They saw his glory in the transfiguration – this is how Jesus will return in glory. Paul saw the glorious Jesus on the road to Damascus. The Apostles passed on the Gospel to the next generation to people like Timothy, etc. They passed on the faith to generations for 2000 years. We have the writings of the Apostles (eye-witnesses) so that we also may believe in Jesus and be saved at His 2nd coming.

The gospel and the hope for the 2nd coming has been passed from generation to generation till today with the same hope that Jesus will come and judge the world.

AD70 was a temporary judgment on Israel. But Jesus did not judge the Gentile nations in AD70, the heaven and earth did not pass away, the dead were not raised, those alive did not get raptured in AD70.

The Church has continued after the Apostles died because God is not done saving people.
The Apostles passed on their Gospel and faith to the people after them.
Every Christian generation has kept the faith in Christ, looking forward to His 2nd coming.

The proof is that we have had billions of Christians over the last 2000 years.
God’s love has been proven right.
God’s decision to delay the 2nd coming has been proven right.
The nation of Israel who persecuted the Church were judged in AD70.
The Roman Emperor, Nero tried to eradicate Christianity but he died. Many other Roman Emperors tried to kill Christians but they were thwarted
and finally Rome converted to Christianity in the 3rd century. The Gentile nations have been hearing the Gospel for 2000 years.
Look at the no. of believers who have been saved in the last 2000 years.
God has been proven right to delay the 2nd coming so that more people may be saved.

But in the future 2nd coming, God will bring judgment to the world and there will be no more salvation. All things will end in the future. The world will SEE Jesus coming..it will not be an invisible event. The world will be judged with fire…and unbelievers will perish in that fire..

Acts 1 “10 They were looking intently up into the sky as he was going, when suddenly two men dressed in white stood beside them. 11 “Men of Galilee,” they said, “why do you stand here LOOKING into the sky? This same Jesus, who has been taken from you into heaven, will come back in the SAME WAY you have SEEN him go into heaven.” 

When Jesus comes, He will resurrect all those crucified Him and EVERY EYE in the world will SEE him…all people in all time will see it happen because the dead will be raised…all at the same time. 

Revelation 1 ““Look, he is coming with the clouds,” and “every eye will SEE him, even those who pierced him”; and all peoples on earth “will mourn because of him.” So shall it be! Amen.”