The mitzva of sitting in a sukka is that the sukka should serve as one’s primary fixed residence for the seven days of the festival.

The Sages taught: For all seven days of Sukkot, a person renders his sukka his permanent residence and his house his temporary residence. How so? If he has beautiful vessels, he takes them up to the sukka. If he has beautiful bedding, he takes it up to the sukka. Likewise, he eats and drinks and relaxes in the sukka. From where are these matters derived? As the Sages taught that the verse states: “You shall live” (Leviticus 23:43), teaching that you shall live in the sukka as you dwell in your permanent home. (Sukka 28b)