TMP should have been set ten years after TOS, but dialog in the film states it's less than three years after TOS' 5-year mission.
...At a
minimum. It certainly doesn't state anything else. And when it does mention, indirectly, that TOS happened, it singles out those five years as a unique event in world history, rather than just a five-year stretch of the hero careers or lives: it seems that nobody else on Earth at that time has done anything even remotely comparable, so Kirk can roll up his CV and clobber all competition to submission with it.
TOS is in the past of the heroes, and this bit of information suffices. It may be in a relatively distant past, too, so that there's lots of nostalgia involved, lots of rejoicing at meeting again at long last, and lots of rustiness when it comes to Kirk's space skills. Plus lots of grey on everybody's head.
But if we go by time references in TWOK then it takes place about 10-12 years after TMP.
Well, neither of the movies actually contains such references. TWoK refuses to acknowledge TMP, and TMP just sort of floats there.
That's plenty of time for at least one more voyage under Kirk.
Or sixteen. But the point of TWoK is that Kirk isn't voyaging any longer, and any mission between TMP and TWoK would detract from that - and the more, the worse.
GEN implies Kirk has commanded an Enterprise (1701 and 1701A) for thirty years
Again, absolutely not. We hear a reporter speak of starships named
Enterprise, from the angle that Kirk has had a stint at commanding each of those in the past 30 years. It's difficult to see how one could read "Kirk has commanded for thirty years" into what is actually being said there, since, well, it is
not said.
"The Menagerie" established it wasn't impossible for someone to command the same ship for several years given Spock states he served with Pike for nine years.
But that would assume that Pike commanded the same ship for nine years, which again is
not stated in that episode. All we learn there is that Pike was the ship's CO at the two times specified - just like Kirk has been in command of the
Enterprise for more than one time.
The first time we learn that Pike (and thus by association Spock) might have been associated with the ship for a great length of time comes in DSC "Brother" where we see in writing that Pike got the command in 2250, and immediately before that was already the ship's XO under Captain April. So yes, it's possible for an officer to get seriously stuck with a single command. It's just that this evidence first surfaces in DSC, where it's included exactly because it has been a fandom urban legend for so long. Until then, the urban legend had little basis in onscreen utterances or writer intent or things of that nature...
Timo Saloniemi