Scary huh? I mean 1995-2001.
But back on the enlisted servicemember "usual" career . . .
Back in the day with the Utopian Roddenberry there were suppose to be no enlisted . . . everyone is an officer. Must have been a lot of over-educated under appretiated ensigns running around.
Then with the movies you start seeing enlisted crewmembers in the background. That's right, those strait up specialist, good at their job, salt of the earth, don't you call me Sir I work for a living type.
But they began to deminish in stature during TNG . . . only to be brought to the forefront with SCPO O'Brien.
So how long did it take him to make E-8?
He joined up in 2346, and ended up being assigned to SFA in 2375 . . . just short of 30 years in his last canon reference.
In 2364 he was a CPO (E-7), and somewhere between the second (2370) and fourth season (2372) he was promoted to SCPO . . . if using the USN style of his rank he would be a MMCS right?
That means it was 18 years to make CPO, and an additional 8 years until he was promoted to SCPO . . . and since he wasn't promoted to MCPO than it at least as much time to be promoted to that.
However, if it works anything like in real life there shouldn't be any automatic promotions post Crewman/Seaman (E-3) if keeping the navy tradition . . . and one can be a PO3 for 8 years from Initial Entry Date (if the present rules apply (and there once was a time when someone could be a career PO3 (OMG!!!))).
Assuming that without administrative holds, that TIS (time in service) requirements are 0 months for Crewman Recruits, 6 months for Crewman Apprentice, and 12 months for Crewman . . . without a command waiver for faster promotions . . . that means from Cn to MMC it takes 17 years to go through the Petty Officer Ranks. That's about 5 years in each petty officer rank (E-4 to E-6).
Must be a hard MOS to be promoted in. If I remember correctly promotion scores needed to reach the next rank are determined by your Rate/MOS.
Therefore you can have a younger SFC 11B than a SFC 68W.
So the breakdown from the information we have is
IET . . . Ct (Constructionman Trainie)
1/2 year . . . Ca (Constructionman Apprentiace)
1 year . . . Cn (Constuctionman)
2 years . . . MM3 (Mechanics Mate 3rd Class)
8 years . . . MM2 (Mechanics Mate 2nd Class)
13 years . . . MM1 (Mechanics Mate 1st Class)
18 years . . . MMC (Chief Mechanics Mate)
26 years . . . MMCS (Senior Chief Mechanics Mate)
This makes sense to me . . . usually most Chiefs get their either within 5-7 years before making their 20, and those who go beyond their 20 and are still moving up through the Selection Boards (which at Chief go servicewide) usually have more than 20, with MCPOs getting close to 30 or having already reached it.
There's also the politics involved once you go to the servicewide selection boards . . . that go beyond your personel file and promotion packet.