I don’t mean all the crews would be of equal status. On a meta level, we’re the PCs so we’re the main crew; but there would be NPC crews for late shift and graveyard shift (or whatever we want to call them) with a Lt. Commander in charge. After all, there is no night in space, and it would be irresponsible to assume that alien cultures keep to day lengths that resemble the Earth-based 24-hour cycle. There has to be a crew on the bridge ready to respond immediately to any threat, even if only to get the ship out of danger while the main crew wakes up and scrambles to the bridge.
What does that mean for our game shifts? If they’re supposed to be the same length as in real life, that’s really fast. I was imagining that each exercise is a full shift length, several hours followed by down time (meals, sleep, admin, physical training, etc) represented by our short breaks in the Mess Hall; and that each mission might take place over several days, where we’re clearly not on duty all the time, but, as in a TV programme, you just show the exciting bits where we get shot at and shoot back.
If all the above speculation is irrelevant because the matter has already been settled in established lore, I’d be happy to hear from someone who knows.