+2 - including the Star San part. I really only break out the O2 for big beers, and I kind of use a rule of thumb of 1 second per OG point - so a 1.090 beer gets 90 seconds, a 1.120 barleywine gets 120 seconds, etc. For beers even up to the 1.070's I don't bother with the O2 tank. A slow pour through my filter screens, followed by a bit of sloshing does just fine.You want the bubbles to come out almost as slow as possible. If it's bubbling out the top of the wort, then it's not going into solution.+1
I run mine for around 60 seconds or so. I don't really time it. Bigger beers, I run longer than smaller beers.
My understanding is that it is extremely hard to over-oxygenate.
I also keep 5 gal star san around and start and finish the process in the starsan to insure i done leave or clog the stone with wort. They are really hard to clean if ya get wort in them.