Palace Chase is always an option. There's two ways to go about it one thru the Force Shaping Program, which I think you, might be asking about and the other is thru the SECAF. Both use the same paper work; the only difference is who approves the application a Full Bird at AFPC (i.e. Assignment Section Chief) or the SECAF. The only caveat to the SECAF route is that it is a 3 for 1 swap instead of a 2 for 1 swap under Force Shaping.
A good rule to go by for a date of seperation from active duty is usually one year from your ADSC ending. Anything more and the AFPC usually squawk about your time remaining. Usually if you get to that point you can 7 day opt any assignment they give you and stay put for that year and then get out without any strings.
Just speaking from experience!!!