You have said, “I believe it (the rapture) is set to happen when a specific number of born again believers is reached, and I base that conclusion on my understanding of Romans 11:25.” When I read that my heart suddenly sank. So if I have just now given my life to Jesus, will I still get left behind?
Romans 11:25 says Israel has been hardened in part until the “full number” of gentiles has come in. Researching this verse led me to believe that the Church will have a predetermined number of believers, which Paul called the “full number”.
I learned that he was borrowing a nautical term that described the total number of crew members necessary for a ship to legally set sail. As soon as the full number was reached, the ship was immediately cleared to leave port. This is why some captains scoured the bars late at night for drunks they could kidnap if they were a man or two short of their “full number” when it came time to set sail.
If so, that means when the full number of the church has been reached, the rapture will immediately take place. This explains why no one can accurately predict the date of the rapture. Only God knows what the full number is and how close we are to reaching it. Since you became a believer before the rapture you are part of the full number and will not be left behind.