Originally Posted by reinballe

I would always ask FA to do this. May not be a good idea to do it yourself.

This reminded me of a UA FA I meet in Rio a couple of years ago. She had travelled there for free from NRT. On the transpacific segment she had been sitting in (and blocking) a lavatory for the entire flight. (Slightly disturbing for a number of reasons).
Flight was full, but she was allowed on, as she could sit in the crew rest seats during takeoff and landing... then the lavatory the rest of the way.