WY,just wondering did you do some fasting yourself ?
My personal experience is from 14-21 days fast only(I cannt dedicate more personal time at the moment for fasting, hope temporary).
I have never fainted or felt really really weak. I am not sure whether my fasts are exactly long fasts (I dont feel they are long either ) but definatelly are longer than 3 days. I had some detox symptoms after the first week so I know I need more than 3 days to work on my health issues