3 days of altitude discomfort at 8,200 feet is not a good sign for the effect at 13,000. I did a fair amount of research in 1999 in connection with the Whitney climb, particularly as a possible prelude to Kilimanjaro (19,340) sometime. Altitude sensitivity varies by individual and cannot be overcome by fitness or training. Some people just need more time than others. <BR> <BR>In my case I have no discomfort sleeping at Mammoth (8,000) and skiing lift-serviced to 11,000. I will run out of breath faster the first couple of days. I am reasonably acclimated on day 3, as evidenced by Doug Nidever's recommendation for both Adam and me that our backcountry touring (climbing from 10,000 up to 12,000) start on that day. If you're still uncomfortable on day 3, that's evidence you ascended too fast. <BR> <BR>The altitude increments (particularly for sleeping) affect more and more people. My wife was usually OK at Mammoth but had severe headaches for the first 3 days at Colorado resorts over 9,000 until I got her Diamox. At the Whitney camp at 12,000 I was comfortable but still could not sleep. Adam threw up his dinner but fortunately slept some, ate some breakfast and made it to the top. <BR> <BR>56% of Kilimanjaro attempts are successful, but most try it in 5 days. If you allow 6 days the success rate goes up to about 75%. I am convinced that Mauna Kea requires acclimatization for 90+% of skiers, but the logistics of arranging it are difficult. A quick trip to the observatories for an hour or so would be doable like my drive up Pikes Peak, but you'll still be resting and popping pills for several hours afterwards. <BR> <BR>Another interesting point is that adolescents are generally more altitude sensitive than adults. It was more difficult for Adam to climb Mt. Whitney at 14 than me at 46.