Interestingly, she was ill recently and had to hand the running of the ship over to the rest of the bridge team.
We were on a ship recently and did a behind the scenes tour. The Captain wasn't on the bridge when we got there, but the staff captain was. There were another 3 officers on the bridge as well as 2 lookouts. The Captain came out of his cabin part way through the tour (also looked like his was just off the bridge, like Captain Kate's).
On Celebrity, the Captain (and probably most of the senior bridge team) do three months on, three months off. As Shuffle says, the captain makes sure they are on the bridge for all the major manoeuvres, but on port days and sea days they do shifts, just like the rest of the crew.
I imagine they prioritise day shifts over night shifts though, purely because their role also incorporates some guest interactions and dealing with the hotel staff side of the ship too.
I also follow RachelMayAtSea on instagram. She was on Captain Kate's Beyond all-female startup bridge team and is now with P&O. She is a Safety Officer (and is also now a qualified Master mariner), so has some really interesting videos on the safety behind the scenes, like lifeboat drills and training and the MES escape systems).
P.S. @Standingupstandingout what programme was it you were watching? Just in case it's one I've missed!
As a cruise lover, I find all the behind the scenes stuff fascinating (the most interesting bit on our recent tour was the laundry!). There's a new Disney+ show called The Odyssey with Joshua Jackson channelling his inner ER era George Clooney. It's total cheesy trash and totally not like a true cruise, but somehow totally engaging! (Though that might have something to do with the JJ/GC point above!)