The Bible does not place a specific limit on the number of people who can enjoy spending eternity with God in heaven. Everybody who asks receives, and everybody who seeks will find (Matthew 7:8). There is no spiritual distinction among those who have placed their trust in the righteousness of God (Romans 3:21-22). The Apostle Paul says without setting forth any categories that our citizenship is in the heavenly sanctuary above (Philippians 3:20). Jesus Christ said that the "household" of the Father is comprised of "many rooms" (John 14:2-3).
If the Jehovah's Witnesses are correct in their understanding regarding the 144,000 people spoken of in Revelation chapters 7 and 14, then that would mean (in order to remain consistent with the rest of the context) only a small remnant of Jewish people could be saved. With that point comes other inferences that are ludicrous. Charles Taze Russell would be excluded from heaven because he was not a Jew. The Apostle Peter would be excluded from heaven because he was not a virgin. All women would be excluded from heaven because the context identifies all members of this group to be males (which would be sexist).
These believing Jewish males could very well be ordained by God from the twelve tribes of Israel to preach the gospel in the midst of tribulational calamity (Revelation 14:1-3). Other commentators take this reference to the 144,000 to be a symbolic representation of the entire body of the saints. After all, Revelation 7:9-10 says that countless multitudes of people were standing before the throne of God worshiping and singing praises. Nonetheless, the idea that only 144,000 people will enter heaven is untenable.
Strangely enough, the idea of an eternal paradise earth for a secondary class of believers was introduced into the Jehovah's Witness sect by Joseph Rutherford, the second president of the Watchtower Tract and Bible Society. It was not taught by Charles Taze Russell, who is reputed to be the founder of what has been termed the Bible Study Movement. This teaching has not been present among the Jehovah's Witnesses from the very beginning.