The other six churches are viewed as picturing the Church during these periods:
Smyrna - (Rev. 2:8-11) - The persecuted Church - (circa A.D. 100-312).
Pergamos - (Rev. 2:12-17) - The state Church, Satan's seat - (circa A.D. 312-606).
Thyatira - (Rev. 2:18-29) - Roman Catholicism, Jezebel - (circa A.D. 606-1520).
Sardis - (Rev. 3:1-6) - Protestantism as a Remnant - (circa A.D. 1520-1700).
Philadelphia - (Rev. 3:7-13) - Love of fellowship and soul-winning - (circa A.D. 1700-today).
Laodicea - (Rev. 3:14-22) - The Christ-less Church - (circa A.D. 1900-today).
Of course, the seven churches mentioned by John were literal churches in Asia Minor. But, much like the seven Feasts of the Lord, found in Leviticus 23, God often has a double meaning for His Word. Jesus fulfilled the Passover (1 Cor. 5:7); He was the Unleavened Bread (Jn. 6:48); rising from the dead, He was the First Fruits (1 Cor. 15:20). The Feast of Pentecost was a feast of the harvest, and, since the Church began on Pentecost, and since our "job" is to harvest the fields ripe for the harvesting, the Church is the fulfillment of the fourth feast (Jn. 4:35). I am 100% confident that Jesus will literally fulfill the Feasts of Trumpets, Atonement, and Tabernacles, with His Second Coming!
The reason that there are two churches co-existing at the same time, is that today, there is the organized religious church, professing faith in Christ while excluding Him from being Lord over their lives, and the Body of Christ, which is more an organism than an organization! It is composed of genuine, born again believers, who recognize that Jesus is Lord of their lives. According to Revelation 3:10, the genuine believers will be removed prior to the Tribulation via the Rapture of the true Church (Jn. 14:1-3; 1 Thes. 4:16-17; etc.)! The Church, as pictured in that of Laodicea, will continue to exist during the Tribulation, and many of the martyred will be members who finally realized they were not saved!
The Church Age ends with the beginning of Daniel's Seventieth Week (Dan. 9:27).