The Apostle's question to the Lord Jesus in the Olivet dicourse was in regard to what would happen at the end of the age:
"'Tell us,' they said, 'when will this happen, and what will be the sign of your coming and of the end of the age?'" (Mt.24:3).
Earlier the Lord Jesus told us what will happen at the "end of the age":
"Then he left the crowd and went into the house. His disciples came to him and said, 'Explain to us the parable of the weeds in the field.' He answered, 'The one who sowed the good seed is the Son of Man. The field is the world, and the good seed stands for the people of the kingdom. The weeds are the people of the evil one, and the enemy who sows them is the devil. The harvest is the end of the age, and the harvesters are angels. 'As the weeds are pulled up and burned in the fire, so it will be at the end of the age. The Son of Man will send out his angels, and they will weed out of his kingdom everything that causes sin and all who do evil. They will throw them into the blazing furnace, where there will be weeping and gnashing of teeth. Then the righteous will shine like the sun in the kingdom of their Father" (Mt. 13:36-43).
Here we can see that the Lord Jesus speaks of a harvest that will happen at the "end of the age." He also makes it clear that the harvest will take place in the field, and He says that the "field is the world."
This passage alone destroys the teaching of the Preterists who assert that the "end of the age" happened in Jerusalem and Judea in 70 AD because there was no world wide harvest that happened in that year or anytime since.