There is no need to assume that the 144,000 Jews will be taken off the earth prior to the end of the Millennium. Since they are sealed for protection, I see them as remaining and surviving on earth throughout the seven years of Tribulation. I suspect that after the worldwide evangelism, which will take place in the first half of the Tribulation, they will migrate to the city of Petra for the second half of the Tribulation. They will be among the Jews who welcome the return of Yeshua at Petra, then enter the Messianic Kingdom with Messiah and have a special role in the Kingdom as spelled out in Revelation 14:1-5. After the Kingdom, with all believers, they will enter into the eternal order.