Time: People said we were super tough to do it in a day. Matt just said he spent 20 days up there. I'd say he and his lady are the tough ones! I'm too old and lazy to camp. Seriously though, sleeping at altitude is very debilitating. Coming out of the Canaleta, we were passing people on the summit ridge like they were standing still. That's because they almost were: we were well rested, while they were shot. I believe the traditional advice should be reconsidered (read next).
Acclimatization: Most of what we've heard is old wives tales; the science is different. There is a very high variability in people's response to altitude, and a number of conflicting factors at work, but here are two quickies:
1) For most people, it is far better to go as high as you can, as fast as you can, and then get out of there even faster, rather than move slowly; that traditional method simply exposes you to the deleterious factors longer. But if you can't get out of there fast, you're screwed. It's all or nothing.
2) It takes 19 days to make a red blood cell.
Chemical Heat Packs: We used the same thing you'll find in REI or any hardware/hunting store: air activated (iron). Work great. Big mittens/boots insulate, but if your hand or foot is already cold, insulation has no effect, so don't even think of comparing these. Heat packs ADD warmth, which the most massive insulation cannot do. As someone noted, the higher you go, the less oxygen, so the less heat, but that's almost better; they are normally too hot, and the low O2 means they last longer.
Falling to your death while sitting down on ice wearing slick nylon pants to adjust your crampons: Definitely happens. I don't recommend it, as stupidity is often fatal in these environments. A great partner is probably the safest piece of equipment you can have, followed by training, experience, and judgement. Equipment would be #5.