I'll see that

and raise you a

and a

.
Those assertions are not rooted in canon.
Kirk was never established to be the youngest officer to make Captain on screen. It was part of the character background information developed for the show. He was thirty-one when he was named a Captain according to his
entry on Memory Alpha, but it cites no source. (I suspect it has been allowed in since it is such a closely-held fanon fact and
did come from background information.)
There was some reference to
Tryla Scott being the youngest officer to make Captain at the time of TNG's 'Conspiracy' some 100 years later. She presumably made captain at 27 to outdo Picard's 28 when he is believed to have taken command of
Stargazer.
The only starship class vessels (as we canonically don't know that they were called
Constitution class) we know that were destroyed with all hands on five-year missions in TOS were
Constellation and
Defiant. I'll give them the benefit of the doubt and assume both were on a five year mission. That's two. Likewise, the crew of the
Exeter was killed but the ship was presumably recovered. That's technically three, but not a lost ship. The
Excalibur was wrecked by the
Enterprise herself during wargame M-5 tests in 'The Ultimate Computer,' not lost on a five-year mission. That's one destroyed, but technically not while on her five-year mission.
That's three crews possibly lost on five-year missions, and three ships destroyed. According to Kirk there were twelve like the
Enterprise in the fleet. That leaves nine including the
Enterprise. TOS-R tells us the
Intrepid was also a starship class ship, so in retrospect when it was destroyed by the space amoeba it too may have been on a five-year mission, and that's TOS-R.
That leaves eight, including the
Enterprise, that may have completed their missions. And that assumes there weren't other starships similar to the starship class on five year missions, yet not similar enough to be counted as 'like the
Enterprise.'
I believe it was the non-canon 'Mr. Scott's Guide to the Enterprise' that suggested the idea that the
Enterprise was the only ship to make it back originally, based on the adoption of
Enterprise's ship insignia fleet-wide. Personally I find holes in this logic the size of a
Galaxy class.
Eat that sisko... you are just a gay ass pansy compared to Kirk...
"Laddie... don't you think you should...
rephrase that?" For so many reasons.
