If your event happens more frequently than once per month, then it shouldn't show up there at all. This is because If everyone was allowed to post their weeklies, the events tab would be filled with weeklies everywhere and the major events would get lost in it.
And we're about to discontinue ANY weekly on the events tab since we have the stream tab now.
This doesn't stop you from making weekly threads, however. They just can't be posted as events.