I came across this snippet in Chris Bonington's book Annapurna South Face, and thought of you:
> In light of our experience on the South Face, I should not recommend anyone to encumber himself with oxygen equipment for use while climbing or ferrying on mountains of up to 26,500 feet; but it is as well to have some oxygen in reserve for medical purposes or for a last-ditch effort similar to my own ferrying on the South Face of Annapurna.
He's talking about multi-week, siege-style ascents of much bigger mountains, and I don't know how '70s oxygen kit compares to today's consumer oxygen cans in terms of benefit-per-weight. But I think that argues for oxygen cans not being worth the extra weight and hassle.