Here's a random idea, and I don't know how popular it would be and what not-
I always love mingle posts! But after a few days it gets bumped down and forgotten beneath other posts. Maybe for the duration of the 4th wall event, is it possible to sticky the mingle post to the top? Then it wont get buried, will be a constant reminder to everyone that 'hey! People are still posting here', and might cut down on too many posts if people see it still getting used?
As a alternative thought, two mingle posts might work too. A morning and afternoon one?