Howdy,
I think, AAdvantage is doing this.
Year n you are EXP - get 8 VIPOW's. (Year n = 1 Jan - 31 Dec of n).
For each year n+x you get 8 VIPOW's. Thus, regardless of if you qualify on 1 Jan of n (yes, it's not possible) or you qualify on 31 Dec of year n - you get 8 VIPOW's for that year. Then - as you are always EXP for n+1 you get 8 VIPOW's for n+1, should you requalify during n+1, then you get 8 more for n+2.
Generally, the begining and end balance I think.
YMMV
Keep the faith,
Pakse