An idea that brought up this subject is here, a quote from a description of ENTJ: "Feeling in this type appears most authentic when implied or expressed covertly in a firm handshake, accepting demeanor, or act of sacrifice thinly covered by excuses of lack of any personal interest in the relinquished item."
Aged 31, I don't consider myself - or the people of my age - generally "immature" with their 3rd or 4th function. Some are, yes. I've had an extreme experience of Fi due to my recent burnout, from which I have recovered. I felt a lot, thought a lot.
So what do you say, how are the 3rd and 4th functions displayed in a good manner - if however weak - in any of the types you know?