I believe that I remember Goenka, in one of his videos, saying that once you feel a free flow of energy you should stop sweeping from top/bottom and go left to right back to front to check for stagnation. If there is nothing detected then switch to whole body awareness. 

For some reason, I think I heard this on an online talk so I started listening to his 10-day talks on youtube and even searched the transcripts. For the life of me, I can't find it and was hoping someone knew where this information is located if he mentions this.

Thanks,
Jorge