I am re-watching TNG for the first time since original airing and something is bothering me that didn't as a kid.
How long is a shift for senior staff? Is the bridge rotation every 8 or 12 hours? Is there an in universe answer for this? As it seems that all of the senior staff are on the same shift (which seems very very weird) who is on the other shifts? Or do shifts overlap and so it just so happens that a majority of major items happen during these overlaps?
According to the TNG episode "Chain of Command, part I", the Enterprise has three duty shift rotations, presumably of 8hrs each.
A small subplot of the episode revolved around changing that from three to four shifts as Captain Jellico
who had temporarily replaced Picard, prefers the latter.
Quotes from the script:
JELLICO: How many duty watches does the crew stand?
RIKER: We're on a standard three shift rotation.
JELLICO: I'd like to change that to four starting tonight.
The reason that all the senior staff are always on the same shift, is that the series always follows them, thus we as viewers have a biased view.
This is addressed in the Star Trek: TNG Technical Manual.
Critical operation areas such as Command, Engineering, Medical, etc will run three shifts of eight hours apiece; Day Shift, Second Shift and Night Shift.
Non-critical operation areas (presumably those in research areas like Exobiology, Life Sciences and Geology) will typically run a two shift pattern; Day Shift and Second Shift with all of their team members rotating off for Night Shift. This allows them greater interactivity and regular team contact as well, presumably as being a more family-friendly working environment.
During Cruise Mode, ship's primary operational personnel are organized into three distinct working shifts. Each shift is assigned to duty status during one of three eight- hour work periods. Primary operations are defined as those functions that must be performed or enabled at all times. These are generally to insure the spaceworthiness of the vehicle, environmental support, propulsion systems operations, and the ability to perform primary missions.
Other support functions including secondary mission operations are not necessarily required to be maintained on a twenty-four-hour-a-day basis. Many such departments will confine themselves to one or two operational shifts to increase the interactivity among working personnel.
As to the question of why everyone's always wide awake, we can reasonably assume that the Captain (with the support of the Operations Office) selects warp speeds and routes based on when the ship will arrive at destination with the goal of maximising operational awake time for non-critical science teams and minimal disruption to normal working schedules for command staff. There's little point arriving at Planet X at midnight and having to wake up the entire geology team to do a survey when you could simply increase your warp speed by 1 and arrive at 8am when they're bright eyed and bushy tailed.
This forward planning would also explain (at least partially) why all of the senior staff are usually present when they get somewhere worthy of an episode.
