R U sure it's "Free" @ Essendon after hours?
When the tower closes after hours, control is delegated to Melbourne Radar / Tullamarine. It doens't become a CTAF(R) like Moorabbin.
Note too, I see Moorabbin tower is opening at 9am these days. They get a sleep-in at the moment for some reason. Perhaps they are staying later because it's busy. When it's not smokey at the moment it's a hive of activity with everone desperate to catch up on their lessons. Last Friday was the busiest day I've been flying on for over a year. On the down side more beacons went off than ever before. The Dornier (Rescue 431) was seemingly tracking beacons all day.