MikeH, those climbs in the months before are good for conditioning, but not so much for altitude. On your Whitney hike, you were at altitude for less than 24 hours, and that's about the right amount of time for AMS to just set in.
Couch is going to be at 8k in Mammoth and at Whitney Portal for 3 nights before heading up, so that gives him an extra 48 hours, which is what most people need.
