Lulsgate Bottom Institute for the Terminally Depressed, or Bristol as it's more widely known works 5 watches of 5 (or at least we're meant to, whether we will ever get there is up for debate!) on a 6 on, 1 sleep, 3 rest pattern.
And before the 'know it alls' start harping on about us being NATS, we had the same structure long before we entered the Hotel California.