I voted yes to backing off a quarter turn since it was the closest answer, but like many, I just back off slightly from fully on, perhaps it's like 1/10 to 1/8 of a turn.
I was keeping it on fully for a couple of years, but it caused a lot of confusion in other people and I had my valve turned off twice by DM's, although I caught it before I splashed. I eventually went back to the slight backing off.
I had a new issue last week in Grenada. I went to turn my tank on before putting my rig on and it wouldn't loosen, so I asked the DM, "Did you turn it on?" He said "No", so I tried to turn it to the right and it wouldn't budge that way either. I tried again to loosen it, and I couldn't budge it. I tried as hard as I could, and it finally opened. If I wasn't in the habit of making sure, I could easily have believed it was already open, though it would have been caught on my next test of breathing while watching the pressure.