Tom and Nawang slept there without the use of supplemental oxygen to acclimatize successfully at that altitude. This means they are now well-positioned to proceed up to Camp IV at 26,082ft. on the South Col when weather permits. From there they will eventually make their summit attempt later this month when snow and weather conditions are optimal.
Right now, high winds and deep snow are still preventing teams from moving higher on the mountain. So Tom and Nawang are taking this opportunity to descend the mountain and trek down to a lower altitude to rest and restore their bodies for a few days. High on the mountain, the air is too thin for normal regeneration and strengthening. Even small cuts and scratches on one's skin will not heal quickly. Trying to go higher now would actually diminish their chances to reach the summit.
The only way to regain strength is to descend to lower altitudes. They will hike for two days down to the beautiful village of Deboche (12,370ft.), surrounded by blooming rhododendron forests.
Conventional wisdom is that that once climbers can successfully spend the night at Camp III without using any supplemental oxygen, they are sufficiently acclimatized to attempt the summit, though this is not a guarantee. As they rest at Dewoche they will lose little of their acclimatization, but gain a great deal of strength that will be needed later. The final day's climb to the summit from the South Col will involve a long distance and a large altitude gain (see chart above).
Here's a close-up of the summit pyramid of Everest. After acclimatizing to the altitude of Camp III, in order to have strength to get to the summit, climbers must leave here...
...and descend to an altitude such as this near Deboche to allow their bodies to effectively recover and restore. Bonus--they will enjoy hearty appetites, sound sleep, and the spectacular beauty of the area's rhododendron forests in full bloom right now before having to return to the bleak snow and ice of Everest.
© McMillan Associates 2004-6. All rights reserved.
Tom and Nawang wisely tested their oxygen systems soon after arriving at base camp. This allowed them plenty of time to replace any malfunctioning items. Supplemental oxygen is heavy to carry and is used sparingly, generally only from the South Col to the summit.