I guess it mostly depends if the owner allows it, and then it’s a the discretion of Captain and chief stew. They also used guest cabins to quarantine crew members on a few occasions.

BD season 8, Francesca gets pissed at Elizabeth for sleeping in a guest cabin with James without asking for authorization. Francesca and Lee state it’s at the discretion of the Chief Stew and Captain. Kate also slept in cabins a few times, the crew asked her as well, they even damaged a panel in the master cabin on Valor. They even turned a guest cabin into a crew cabin because it was connected to crew mess via the laundry room on Eros, season 3.

BD Med: Conrad tries hiding from Hannah and locked himself in a guest cabin, but it’s the last night.

BDSY, it’s either edited out or maybe Daisy is a bit more relaxed as long as they clean the cabin afterward.

BD Adventure: Nate asks Faye to sleep on a guest cabin the last night.