My understanding is that if you are within 100 miles of any level, you will be advanced to that next level. I could be wrong.
I've got two mileage runs next week. PHL> PHX> SEA (RT), overnight. And PHL>FLL (RT) same day.
Under $500 total and it will put me at 100,483 (90,483 BIS) miles for the year.
I need to get the Citibank card as well (I have Barclays silver) next year or start flying J more often.