I waaant to try reading along, but I’m using September to finish up some manga volumes I’m reading. So at best I might try the free preview of chapter 1 to see how it goes for me in October.
As for new threads, one of the earliest (and longest) book club reads, the Aria manga series, retained a new thread each week throughout all 70 chapters. The first thread had 149 comments, and the last thread had 25 comments.
Another early book club, the Yotsuba&! manga series, went with one thread per volume. The first thread thus garnered 936 comments, with the most recent thread reaching 130 comments after the volume was finished. (Note that both clubs’ first threads have also had comments from readers starting the series much later.)
My Sailormoon book club does one thread per story arc (about three volumes length), but that only has a few readers, and minimal conversation.