I wrote in this question in part for my own training but also because of the lack of pack carrying endurance I find on Mt. Aconcagua, where I work. Even the climbers that come in good shape, having trained for the climb, seem to fall apart above base camp when they have to carry their 18-22kg pack above 4,400-meters for several days in a row. There are obviously a million factors that come into play here, but I would love to be able to give future Aconcagua climbers some tips so that they come to the mountain better prepared.