Splitting the metrics between new registrations and returning logins is the right way to test dnsPacanele's claim about engagement. A short repeatable format does seem to fit a community server better than one long session, and it lets people drop in around their own schedule. One thing I'd watch: a themed event getting visibility depends less on the calendar window and more on how clearly the reward loop reads to someone who hasn't logged in for months. If returning players can't grasp the activity in a sentence, the timing won't save it.