I was very unsure when I carbed this beer, so I made damn sure I had a good seal and played around seeing how much the pressure fell each day at the colder temperatures. I think the next time, I might go to 25-30PSI, leave the think alone, and turn the thing off until it falls to where I want it.
If I plan to be drinking the beer after carbed, I will leave it on until I am done, but if you don't have leaks, it doesn't matter.
The pressure gauge will do all kinds of things in the off position. Don't worry about it if you are not leaking.
Just another note, I am using a Corny Keg that will take a bunch of pressure.
This beer foams like hell with the six row, but if I let it sit for a minute or two in the glass with the keg carbed at around 11-12 PSI, it is yummy as hell.
I actually decided to call it "Mr. Toad's Mild Ride" as a play on the old Disney ride where Mr. Toad had the huge foam on the beer mug at the end.