The last time I flew from Australia to Hono (747 business class), there was an affluent appearing older couple right behind me...once aloft, the man got up and went to the can and got into a full set of pajamas.
Shortly before landing, he reversed course - having gotten himself his 9 hours sleep.
Turns out they were staying at the same hotel, so I quizzed him about his habit, and he replied that's the way he's always done it on longer flights.
Wasn't me - don't wear pajamas.