I'll kick in with a few observations: You have 6 quarts over the normal 4 so that is a 50% increase. The filter will do its job of filtering crud and the negligible metal bits out of a newish motor. S&S recommends an oil change every 3,000 miles and on a bike with an oil tank of 4 quarts that is probably a good idea. I've had my 2012 M3W hit 5,000 miles before a change (I'm not proud of that. Pure forgetfulness!) and it did quite well. Discarded oil looked good, pressures were fine but I think the biggest hit may have been the increased acidity of the oil.
As for oil loss, I would look at the valve cover gaskets first. I've never had any evidence of oil on the ground but plenty of signs that the valve covers let off some excess pressure.
I might lose a quart between changes. I really don't worry as we have a lot of buffer room.
Just make sure you change out the oil before you store it for winter! Old oil bad. Too acidic! New oil good! Just right!
