The effects were still working at 1:50 in the morning last Saturday night for EMH.
I should note, though, that we still ended up waiting half an hour or so to ride the thing during EMH, despite getting in line at 1:45 in the morning.
Summer EMH wasn't really all it was cracked up to be. So many attractions had been shut down due to staffing issues, including Splash and Thunder, that the queues for Space, Mine Train, and others were nearly as bad as they had been during the late afternoon, even with no fastpass reservations to slow them down. It wasn't at all the walk-on-and-ride fest that we had hoped it to be.