After a bit of digging, it appears that my last post was pretty close to the truth. The current situation appears to be that the D-i-S Benefit within AFPS 75 has been raised to 3 times pensionable pay from Apr 05. Meanwhile, as an interim measure for Apr 05 to Apr 06 only, for death in that period the AFPS benefits for members of AFPS 75 will be calculated as the best of AFPS 75 or AFPS 05; in effect they would almost always be based on the 4 times pensionable salary given by AFPS 05. Hence, for that transitional year, your current AVC would buy no extra benefit. From Apr 06, you will either have transfered to AFPS 05, and hence your AVC would be unnecessary, or you would remain in AFPS 75 with the "3 times". Your AVC would presumably then need to be reassessed (if it is still allowed). What exactly will happen on the AVCs from now on remains unclear at the moment.
Ginseng