I spent rather longer than you to be qualified to “conn” (con?) a frigate. 7 years from naval college entry to be qualified. Some of that was warfare training, but several years ashore interspersed with training cruise, a year at sea as a midshipman, overseas warfare training including seatime, and a year at sea watchkeeping under supervision to be qualified. No final exam. Just had to be good enough for the captain to sleep peacefully at night while I ran his ship, darkened, no radar, no comms, in close company with a fleet whilst manoeuvring tactically against another force doing likewiise. I think I earned my stripes.
They do it faster nowadays with simulators and shorter training cruises but end up at the same standard.