There is no need to perform an in-flight RAIM prediction. From memory, once an approach is armed, the GPS navigator will preform a RAIM prediction at about three miles from the Final Approach Fix. The navigator will not go into approach mode unless RAIM is predicted to be available (at the 0.3 NM Horizontal Integrity Limit) for the remainder of the approach. Loss of RAIM annunciation will be inhibited for 5 minutes?, however, RAIM alerts will continue to be available.