10 feet is my standard hose length.
Carbonating at "service pressure" works, it takes a week or so.
"Speed Carbonating" works too.......and takes two days or less, or a half hour if rocking. That said it gives a coarse carbonation, not the smooth head we look for in most of our beers. Don't ask me how this works....above my pay grade.
Soooooo, to do "speed carbonating" I have a dual regulator. Get a blast in there on the high (30 psi) pressure, then hook up to the service pressure. Works.