I though you really shouldn't go above 1.4V.
I don't have problems with temperatures yet, idle 25-30*, gaming 50-55*, few hours of torture test absolute max I've seen 75*.
Thats what i was thinking but looking around all 860 need that extra. I have seen them over 1.6V.
Thats why i got this cooler. Stable i would say 4.125V @4.2 (thats 24/7 
thats whyz.