As your premise is wrong, so is your question. Scripturally speaking, it is not taught that visible candlestick churches are necessarily all saved, as they usually contain tares as well as believers. The church of the Laodiceans was evidently one. And while such may cease to be a candlestick in the sight of God, that does not necessarily mean it cannot retain a form of a church, and as with certain cultic churches they may retain enough truth that some souls may find Christ therein, despite the errors and distractions. Such is the case with Rome.
Can you point to a scripture that precisely defines and authorizes your definition of a "valid church" ?
In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, (Ephesians 1:13)
But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. (Galatians 1:8)
Since one is added to the body of Christ by faith in the gospel (1Co. 12:13) of grace that Paul explained, it is essential that a visible expression of that preach said gospel, versus being accused for preaching a false gospel.
All of the seven churches in Revelation were valid churches, so I submit that they must have been founded by the apostles, or their appointed successors, and conform to:
Though Paul (who was preaching long before he even met Peter, and is later sent forth by certain prophets teachers as Barnabas, Niger, Lucius and Manaen at Antioch: (Acts 13:1-3) likely began these, (Acts 19) it not necessary to be founded by an apostle. While the apostles remained in Jerusalem, (Acts 8:14) some of those of the whole church that went forth preaching the word due to the persecution that arose about Stephen seem to have begun the church at Antioch where the disciples were first called Christian. To whom Barnabas was then sent by the apostles to strengthen them, and who later brought Paul, both of which met with the church there for a year. (Acts 8:4; 11:19-26)
In any case, being founded by an apostle does not mean that such will forever by a true church, any more than being a physical decedent of Abraham means one is a true Jews. The church that the Lord promised would endure is the body of Christ, which alone consists only of those which profess the essential faith in Christ as the Divine Son of God, trusting Him to save them on His account, purifying their hearts by faith.
"Who is he that overcometh the world, but he that believeth that Jesus is the Son of God?" (1 John 5:5)
I write unto you, fathers, because ye have known him that is from the beginning. I write unto you, young men, because ye have overcome the wicked one. I write unto you, little children, because ye have known the Father. (1 John 2:13)
Nowhere does Scripture say one has eternal life or overcomes anything because they believe Peter is the rock, versus Christ. That the latter is the case is the only interpretation that is confirmed, as it must be, in the rest of the New Testament. For in contrast to Peter, that the LORD Jesus is the Rock (“petra”) or "stone" (“lithos,” and which denotes a large rock in Mk. 16:4) upon which the church is built is one of the most abundantly confirmed doctrines in the Bible (petra: Rm. 9:33; 1Cor. 10:4; 1Pet. 2:8; cf. Lk. 6:48; 1Cor. 3:11; lithos: Mat. 21:42; Mk.12:10-11; Lk. 20:17-18; Act. 4:11; Rm. 9:33; Eph. 2:20; cf. Dt. 32:4, Is. 28:16) including by Peter himself. (1Pt. 2:4-8)
The Messiah personally addressed those seven churches in Asia, each as a genuine "church." Similarly, the Apostle Paul personally addressed the church at Corinth. These were bona fide, genuine churches that were part of the whole, the one holy catholic apostolic church, and the scripture testifies to that view, as well as that a genuine church may have its candlestick removed, and spiritual death may come to those Christians who refuse to do the works of the Messiah. Paul testified to the church at Corinth that they are the body of the Messiah. Now ye are the body of Christ, and members in particular. And God hath set some in the church, first apostles, secondarily prophets, thirdly teachers, after that miracles, then gifts of healings, helps, governments, diversities of tongues.
First Corinthians, Catholic chapter twelve, Protestant verses twenty eight to twenty nine,
as authorized, but not authored, by King James