Not too sure - I would have guessed that most of the messages are written once, read by the constant number of participants (say 1-100 or so) and then they disa

Not too sure - I would have guessed that most of the messages are written once, read by the constant number of participants (say 1-100 or so) and then they disappear off the screen and are never accessed again, ever. Maybe a few people will scroll or search, or use some custom extension to load and export the history, but very rarely.