A few weeks back I got in line @ 9am with about 20 passengers in front of me. Check in started around 10:45. I’m Elite and after waiting Suite, Elite lounge area boarding started at 11:30. Lucky to be the first onboard I headed straight to the Sanctuary and was the first to arrive. Within a 1/2 hour most all lounges we’re filled. Some spots were taken from people doing B2B cruises.
hope this helps.