There's something really cathartic about watching a horror movie with the group of strangers, especially when the movie is really effective. It's like a vacuum that sucks the air out of the room and everyone anticipates the next moment of unease.
I had that experience watching Hereditary and though I'm not sure it will be as effective the second time, the emotional breakdown in the first half is so real, I expect it will make for excellent re-watch value. Plus it's the kind of thing you want to share with everyone you know.
Even if, immediately after watching it, I was completely unsettled.