Typhoon,
Your situation is far from average. It's difficult to say what your roster will look like. Depends on fleet, seat and seniority. Days off (not counting vacation) can range anywhere from 7 to 18. Guys flying only ultra-longhaul will be towards the high side. On the 777, since coming back to the line I have probably averaged 9-11 days off per month. While last year 13 days off average might have happened, it certainly isn't happening now. And averaging your vacation in - are you trying for a management job?