On the Mt. Everest thing:
I've heard this as well. IIRC, this was in reference to standard issue SLR cameras, and dated to the late 60's and through the 70's. If you wanted to take a Nikon or Canon up, you needed to send it in for winterizing; lighter and lower viscosity lubricants, etc. Leicas were said to be ready from the factory. I've shot with a factory standard R3 in Minnesota winters with no problems for many hours on days that had highs of -20 F. The camera was kept exposed to the air for hours at a time with no warm-ups (causes condensation problems), and electronics, metering, and mechanicals all worked perfectly, shooting Kodachrome 25 so you'd know if you were off a significant portion of a stop. I've also shot with the R3 and R4s in 110 F degree weather all day with no problems.
Shot a job for Amhoist outside (the river flats in St. Paul) in -20 F with a Hassleblad 500 C/M(?), and after a short while 1/60th second became about 1 second, then longer.