Have you checked out the Fast Finish in the Learning strategies courses? I've experimented with it and tried it before listening at a normal speed I pushed it to 8 times the normal speed at 10 times I found diminished results. It does add to the listening time but one regular listening brought me the benefit of 2 or 3 regular listening.
It's more of a Genius Code topic and I think has already been discussed there.
Alex
