16 hour shifts....BS. Four hours on the bridge is the standard. Anything else causes huge attention span issues. Been there, done that on several CVNs.
Shoot... 16 hrs was standard. Not all on watch, but I had to go to work after watch and there was flight ops, then UNREP, then Fire Drills, then training, then inspections then gun shoots and then whatever else came down the chain. Somewhere in all that I had to find some sleep and time to play poker. Went a couple days at a time without sleep, or very little of it, all the time.
6 hour shifts port and starboard is standard on subs.