VAHEGURU JI KA KHALSA, VAHEGURU JI KI FATEH
Per the SukhAasan question - The Guru's Darbar is a King's Court. A King has his time of being in his official capacity on his throne and then retires for the night. So similarly, when Guru Sahib has departed from their official seat at the Manji Sahib on the Takht Poash, they retire to their private bed. I don't think the concept of sleep applies, but rather that Guru Sahib has retired from their official Darbaar.
What that has to do Karaah Parshad Bhog/Parvaan does not seem to relate. From what I have heard, this question was posed to Sant Baba Nand Singh Ji, who responded that much as the Punj Pyare were made Parvaan by the Sri Sahib, so is Karaah Parshad made Parvaan with the Sri Sahib.