We notice too that the letters are written to all churches and in all ages. The number 7 of course is a symbol for a perfect church, no matter how many congregations existed or exist. Each will have strengths and weaknesses but they make up a perfect church with Christ as the head. If there was ever only one big church, the letters would have been written to "the church".
The Orthodox already have a perfect church with Christ at its head; 20,000+ protestant schismatic sects many of which have established Christian 'firsts' by allowing abortion, promoting gay clergy, and blessing gay marriage, have neither a perfect church, nor is Christ at their head.
I enjoy Biblical Numerics too. It's really fascinating how they play out in the Bible. Just another confirmation of it being Divinely Inspired. Another point here is that those 7 (spiritual perfection) churches were laid out in a circle on a map, representing the world.