/chatteroff should last across logins; it's saved the same way User Settings are. It should continue until you do a /chatteron.

Hmmm, it doesn't seem to be the case. But maybe that depends on some other user setting, and I must admit I didn't search very deeply. I'll do it ASAP.

Update: it seems that I was utterly wrong, indeed "that" is the case. Still I wonder why I got the impression it was not. With this, I'll add: problem solved!

Also, I'll mention Message Inbox, in case you hadn't found that yet.

Well, of course I did find that, and I was thinking of using it as my entry point, but I prefer to go there only if need be, i.e. if there are "new entries" and notification in a nodelet, as with CB (with /chatteroff) is best suited for my needs in this sense.