I find it the opposite actually. Bitterness creeps in as years go by and you see the optimism of your youth was unfounded, and the sheer amount of hard work you put in school and in your job at twenties leads to bare minimum results (high-paying, stable job but no social life and your reward for being a good, decent, reliable person is "I don't want to be rude, but I don't know you.")Hoo boy, I was not nearly as chill ten years back as I am now. Spock is entitled to a tantrum under his circumstances, I think.
In the end I find myself more thinking like a kid in my 30s (spending time on Star Trek and other entertainment forums, caring mostly about my pet and what comic book/computer game I will enjoy next) than I ever did in my early 20s when I was trying so hard to be "mature" and "adult".
There still wasn't such a drastic change between me at 27 and 35, just more outgrowth of elements that were already there. 35 year old me and 27 year old me wouldn't find each other unrecognizable.
And from personal experience with other people, if someone is throwing tantrums at 27 I wouldn't hold my breath that would go away at 35. I found out the hard way that a lot of people claiming they "matured" or "grew up" is them just hiding those darker aspects of their personalities better...