Some of these replies raise another issue I've been wondering about. Everyone talks about promotions as if they are automatic. However, I talked to a Naval Academy grad who stayed in 8 years after graduation and was only a 1st LT when he left.
Yes, quite likely, someone could be at 8 years and be a lieutenant (O-3), in the Navy or Coast Guard. I think the "1st LT" reference could be something else.
The Navy is a mysterious place, whose use of ranks, jargon, enlisted rating names and billet titles can confound the uninitiated when compared to other services except Coast Guard. In most Navy units, sea or shore, there is an officer, usually a junior officer (Ensign O-1, Lieutenant Junior Grade O-2 or Lieutenant O-3, occasionally a LCDR O-4), whose
billet (job) title is "First Lieutenant." On smaller ships, a senior enlisted leader can also be the First Lieutenant. On a surface ship, the First Lieutenant leads the deck force in the execution of major seamanship functions and the maintenance of topside gear. This can include cargo handling, inspecting and maintaining rigging and deck gear, as well as taking the lead on anchoring, mooring, fueling, towing, transferring of personnel and cargo, and the operation and maintenance of ship's boats. Ashore, the First Lieutenant is who you go to when your office needs painting, for example.
And yes, promotions to O-2 and O-3 are mostly automatic (typically described as, "yep, they fogged a mirror, promote him/her"), as long as their reporting senior checks the recommended for promotion block on their officer fitness evaluations, and they continue to meet all required standards. For O-4, there is a statutory promotion board, when the winnowing gets serious.
More than you ever wanted to know, I'm sure!