Bailed my lovely out of storage and tried to fire her up. So much oil had seeped into the motor that it wouldn't fire upon turn over. It was coming out of the air cleaner and spludging all over the place. Pulled plugs and cleaned. Tried again and it fired and turned over. Oil kept coming out of the breather. I think I may have lost about a half a cup or so. Motor smelled like a two cycle engine for a time. All ok now. Next time, I will drain all the oil before storing!
I know that this suggestion is a dollar late and a day short for "this" time around, but may be helpful next year.
On my old '76 Shovelhead I have nasty sumping when I let it sit for over a month. So I fire it up about once a month so I don't spit out oil all over my floor from the crankcase vent.
But when this is not an option, I purchased these. They work great. Three Piece Lind Clamps
I just pinch off the line between my oil tank and the inlet to the oil pump on the motor. This stops any sumping, totally stops oil from the pump... PERIOD!
BUT... DO NOT START YOUR MOTOR WITH THE CLAMP STILL ON THE LINE.
I know that sounds easy enough to remember, but I always take a string/line from the clamp up to the handle bars and then down to the ignition switch to remind me to take off the clamp before firing up the bike.
It will leave a bit of a narrowing in the line where the clamp was, but just squeeze it on the narrow sides and it rounds out quickly and when warm it goes back to its original shape without any marks at all.
I understand that the S&S has a drain plug on the bottom of the crankcase, but I don't believe they're designed to be used on a regular basis.
So preventing the oil from sumping is by far the best way to go.