That's an interesting thought, actually.
Compare Matthew 28:20: "And, look! I am with YOU all the days until the conclusion of the system of things."
with
Matthew 24:30 - "Then will appear the sign of the Son of Man in heaven. And then all the peoples of the earth will mourn when they see the Son of Man coming on the clouds of heaven, with power and great glory."
How can it be that Jesus would be with the disciples all the days until the conclusion of the system of things [undestood here as the end of the jewish system of things in 70 CE] and yet, in many parables, Jesus portraits himself as going away and then returning?
The only possible explanation, in my opinion, is that the "parousia", the return and presence of the Lord, started as soon as Pentecost 33 CE. If the writings of the apostles seem to indicate otherwise, it is simply because they didn't understand that the "parousia" was already taking place. Because expected the "parousia" to be a spectacular display of Jesus' presence. So, they kept on expecting something that was already ongoing within the invisible realm. When the end of the Jewish system of things came in 70 CE, they should have realized by then that the Lord "had been with them, every day, until the conclusion of the system of things".
They had to readjust their expectations and explanations about the nature of the "parousia".
Eden