A couple of points FWIW.
Flex takeoffs don't have to be to the limit. Even at the limit there is a margin because of the actual temp being less than the assumed temp.
For example we can go 26k,24k,or 22k and within those thrust ratings a temperature flex is also available if the performance is available.
I'm a great believer in compromise in this area and generally don't reduce all the way. Many considerations may apply like runway surface conditions, runoff area,wind, MEL , is this a training flight with a cadet? etc,etc..
Also, as an airline pilot you get to fly with a great many interesting(and not so interesting)pilots from many a varied background. As a First Officer you will continually be fed information from the left seat, all of which can be useful (good and bad)even if the guy is a pain.
You do sim checks and line checks your whole career with different instructors, in my case with a number of different operators, all of whom will endeavour to improve your performance and pass on good experience.
In my short time flying a Learjet I noted that many of the Captains in that world had been so from an early stage and had not done much time in the right seat.As a result they had nowhere near such a breadth of experience and many of their ideas were self developed and guess what - nobody in the right seat was going to put them down so it must be a good idea!
I really think ssg displays these characteristics, a huge fish in a tiny bowl.