I think sleeping is the way that cats use to save their energy or reduce unnecessary energy use. Especially Titan, he saves his energy all day long. And it seems that sleeping is the happiest activity for the whole of his life.
I often find myself staring at Titan & De-i sleeping happily, wondering why I don’t always have a worry-free night’s sleep like them.
In the meantime, De-i She is especially very active and playful before dawn and after dusk; she sleeps to save her energy for jumping, running and playing during the day.