Keep in mind that modern battleships took years to build, even under war conditions when everything is expedited.
I'm going to quibble a bit with this comment.
I originally had some decent details into the construction times of the USS Iowa ( most modern ) with the construction times of the South Dakota class and USS North Carolina ( which was the first battleship built by the US after the Washington Naval Treaty and subsequent London Naval Treaty went in to effect ), but my computer had a brain fart and I lost everything, so you are getting the condensed version.
The actual construction and outfitting of the USS North Carolina, only took 3.5 years, and was plagued with multiple problems:
1) The shipyard lacked men trained in BB construction ( in fact a lack of men in general as the US was still coming out of the Great Depression ).
2) Shortage of steel, because of labor problems.
Despite the issues with the construction of the North Carolina class, the USS North Carolina was completed by April 1941, and as such was not built under war conditions.
The USS South Dakota of the South Dakota class, was built and outfitted in a little under 3 years. Actually built in 2 years it launched in June '41, it's outfitting was plagued by the attack on Pearl Harbor so the subsequent man power disruption and the need to outfit it as a flagship, stretched outfitting out almost a full year. The SoDak was also plagued by the need to shrink and re-arrange equipment originally designed for the North Carolina class. I would qualify the SoDak as built not under 'war conditions', but pre-war urgency, materials are relatively plentiful, and there was a moderate pool of men with some training in BB construction. The USS Alabama ( a non-flagship sister to the SoDak ), only took about 2.5 years, laid down in Feb 1940, and commissioned in Aug '42, I would qualify her as being built under full prewar emergency.
In a nut shell, the USS Iowa was built and out fitted for duty in 2.5 years ( including a redesign of her turrets after construction had already started ), for a class that was larger than the SoDak class, the last ~2/3rds of that was under actual war conditions, but by this time, the US had already built 6 BBs' and so while there was some material shortage, there was a pool of personal that was well trained.
So, while I will grant that under war conditions, build times can be shrunk, it does not take a significant fraction of a mans lifetime, even under non-wartime conditions. The USS Lexington was laid down as a battlecruiser in Jan 1921, construction was stopped while she was redesigned as a aircraft carrier, parts of the ship rebuilt and the ship finished and commissioned Dec 1927 - 7 years total for what stands out as a very unusual construction job.
Even at the height of the Great Depression, when there was a major slow down due to the economic conditions there were several ships built but even then, 3-4 years, saw a ship built and on duty ( the USS Yorktown, laid down in 1934 and was commissioned in 1937 ), and that is less than 1/10th the lifetime of your average man at that time.
The USS Ronald Reagan ( a Nimitz class CVN, with twice the displacement of a WW2 Iowa class BB ), only took 5 years to build, and that was not under war emergency conditions. Heck even the Ford class CVN, is only expected to take 7 years, and they are developing cutting edge tech for it.
Compare that with the 100 year construction time frame for a man that would live ~300 years, in RT, and the scale is way out of sync.