In reply to BusyLizzie:
Hillary and his mates were far tougher and had more endurance than 90% of the foreigners on Everest today. Most Everest clients would collapse on the *approach* to the south ridge of Aoraki-Mt Cook, let alone the climb, that Ed did in 1948. Last November I went up past Gokyo to get a first-hand look at where Hillary and Lowe went over the Nup La in 1952 on their illegal recce of Everest north side. I balked at even attempting the start of it, let alone going over the La and hiking all the way back down east toward Rongbuk. They did this in short time, with big loads. Then returned.
The gear makes a huge difference. Their old O2 sets were much heavier and much less efficient. They were carrying 8kg or more to get barely 2 litres a minute, whereas sets now are a fraction of that and most clients are on 4 litres a minute. They had heavy leather boots that froze, windy canvas tents and weak stoves. The foreigners did the routefinding and rope fixing, with no aluminum ladders or decent ropes and anchors, and carried some of this gear themselves - unlike today. All that work, with that gear, at altitude - it's amazing they made it at all. Their endurance was used up just surviving and doing the expedition work, rather than racing up all unburdened, timed on their Suunto between set camps.
They were just tougher back then. Home life was tougher so expedition life wasn't such a shock. Hillary, Lowe, Riddiford, Cotter and those NZ blokes were used to massive walk-ins up shifting moraines carrying huge packs, making their own way up dangerous icefalls, then doing a big climb on top of that, then walking back home. Most commercial expedition guides who have been in the game since the 80s or 90s will tell you that clients have just got softer and less competent with every passing year.