I’ve definitely had vivid dreams about the FF, particularly about sessions with Fortress Dommes that I’ve never met in person. Sometimes they feel almost realistic that I’ve was sure whether I was dreaming or if this was real life. Some trippy matrix paradox ??
For me subspace highs have lasted anywhere from a couple of hours to 24 hours post session. I recall one time where my subspace high somehow entered into my dream and I dreamed I was back at the fortress (but mentally felt every sensation in the dream session as if it was IRL)