We also wear SmartWool mountaineering socks when it goes below 40 degrees here. The combination of those socks plus the toe warmers might well take care of it for the whole 200K. Pretty sure Chris wore those socks on his last 200--he's also doing his R-12.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks