Here's the thing: Humans sleep 8 out of 24 hours, or 1/3 of the day.
If your "day" is four times longer than our real days, that is 96 hours.
For your book, do you want:
1. Your people can continue the 24 hour cycle, regardless of the position of the sun relative to the planet with artificial light and dark.
2. Your people can evolve and adapt to the extremely long cycle, but still maintain the 1/3 of ther day sleeping pattern, which would be 32 hour of sleep per day.
2. Your people could be like the fairy folk and sleep in a nest of leaves and flowers whenever they are sleepy.
So you need to define the rules for the world that you are creating.
I hope this helps!
