I never know the length of the fast. The true time to stop is when the tongue returns to normal color or the body stops loosing weight.
"IF" we followed the rules, there would never be a need for the second fast or yearly fast, but we civilized humans want it our way, so periodically we need to expel what we ate that accumulated.
My very best book/author of them all, explains to do only one fast in your lifetime. Learn your lesson well and never had the need to fast again. This is very hard to do when we choose to live like the others.