You're welcome.
I might have saved you hundreds of $. If one does infact this route often, one knows there is only 1 flight by 1 carrier who does this non-stop. And it's a daytime flight. One knows that this flight often sells at 10x the posted price ($470 is not uncommon). It's a great deal. It is extremely limited. If you are flexible it's fantastic. You can't fly to BWI this cheaply. You can''t get a buddy pass for this cheap.
As for my mileage varying, "per google flights" I see availability Nov 2, 4; Dec 9, 14; Jan 10....