As an introvert social interaction drains my mental energy so at some point you start investing more energy into enjoying your best friends than into making new friends.
2. There is this recruiting problem where you have to decide which secretary to hire before having seen all of them. The optimal solution is to see the first 37% (1/e) and then hire the first that is better than the previously seen best.
Putting that into lifespan of ~75 ys and assuming we don't really start sampling until we are 15, we end up with an optimal stopping (= exploitation) age of 32.07.
Surprisingly close to the 30 mentioned.
I figured, that for me, 37% (1/e) worked out to 13 people.
This (finding people) is a space I've spent a lot of time doing, planning, understanding, and thinking about :)
Also, there are a lot of scientific papers on how to model these in scholar.google.com (sorry that I don't have links that I can give right now)
I'm not an expert on psychological motivations, so I can't speak to the feelings or motivations of others, just myself.
Most of the time these results are things I find during introspection after social events are over. I can spend 4 hours in a social situation and be one of the drivers that keeps things going. It's later, when I'm alone and meditating, that I discover just how exhausted I was.
My wife is an introvert and is highly skilled at chit chat. She can work a room better than anyone but the most gregarious salesman types. She will remember the names of people that she met 10 years ago, details about their careers, their children's names and what their children studied in college. Doesn't matter if it's a professional event, a wedding, or a funeral, she is always on her game. BUT, she always goes home exhausted.
Have you ever wondered if deep inside you are an introvert that just got very good at pretending to be an extrovert at early age due to social pressure? Western society rewards extroverts.
Are you sure about that? I get the impression that the English culture regards extroverts as freaks of nature and terrifying monsters.
My older male friends are less and less interested in romance as they report finding sex with no strings attached is getting easier with age.
For older women, the situation is the exact opposite. Their dating pool, which consists of (say) all older men keeps decreasing with age.
That might explain why your older female friends find relationships harder as they age, rather than a decrease in their physical attractiveness. The latter is what many women attribute their situation to, but IMO its just statistics and preferences.
But what's also true is women tend to want to settle down in their early-mid 30s (at least in large American cities, among professional types) and now they become simultaneously more selective. In a sense, women are always the 'choosers' with rare exceptions. Men tend to have wider nets, on average.
And this is where Facebook tries to seduce you. I'm going to go ahead and say that 90% of your Facebook friends aren't friends but rather they are acquaintances. Being friends means actually doing something together. Rather than liking your Facebook friends' vacation pictures, why not go on a vacation with them?
In my early 20's, I was more open to hanging around people I know I didn't like, or wasn't compatible with, because I didn't want to be alone or without friends, craved attention, and saw every social encounter as a stepping stone and potentially valuable.
Now, I know better. When you get older you realize you don't need to surround yourself with people whom you don't like, no longer crave as much attention, and already stepped along many of life's stones. You also put on less of a pretense to others and care less about being liked. It's more important to be authentic and true, even if that means having less friends, than a phony with a lot of fake friends. All this has the result of making it more difficult to randomly find real friends.
It's common I'll meet many new people but the ones who I stay in contact with are few and far between, and that's okay. People come into your life and go out of it, it's just the way things work. I'm thankful for everyone I've had in my life and know that there are many more great people who I have yet to meet.