Paul assumed that Jesus would return before Paul died. Of course, Paul was aware that no one would know the day or the hour or Jesus' return (Mt 24:36). Nevertheless, Paul and other early Christians expected Jesus to return soon (see 1 Thes 4:17; Rv 1:1) — in the next few years, if not in the next few days or hours.
Many people think that, just as Jesus did not return in Paul's time, so Jesus will not return in our time. This is illogical. "Note this first of all: in the last days, mocking, sneering men who are ruled by their passions will arrive on the scene. They will ask: 'Where is that promised coming of His? Our forefathers have been laid to rest, but everything stays just as it was when the world was created' " (2 Pt 3:3-4). "This point must not be overlooked, dear friends. In the Lord's eyes, one day is as a thousand years and a thousand years are as a day. The Lord does not delay in keeping His promise — though some consider it 'delay.' Rather, He shows you generous patience, since He wants none to perish but all to come to repentance" (2 Pt 3:8-9).
Paul expected Jesus to return in his lifetime. Jesus did not return, and Paul died in Christ and was taken to heaven. Many people today don't think Jesus will return in their lifetimes. If they are wrong, they will probably not be prepared for His coming. If they are right and Jesus does not come back in the near future, these people still lack the attitude necessary to live life freely, courageously, and fully. If we do not expect Jesus to return soon, we may lose out not only in the future but also in the present. However, to expect Jesus to return soon is an all-win situation.