When young I was definitely an extrovert and got my energy from being around people. I never needed time alone to recharge. I frequently would have parties with 30 people. Since I have gotten older people tire me out and I need time alone to recharge.
I can identify with this. I started my career in technical ranks, got an engineering degree and went further down that path, Then I switched into commercial areas - marketing, sales management, business management etc. I was assessed as ENTP under Myers-Briggs and definitely drew energy from being in a crowd. I was at the extreme end of the scale on Extroversion.
However, much of my early life had me doing things on my own. I did get lonely often. However, in truth, I have never sought to have a bunch of friends throughout my life as my siblings have. I was also very shy and unsure about how people would see me, albeit I had enough arrogance that when people in authority told I would never be able to do something, I delighted in proving them wrong.
When I told a psychologist who was working for me at one time, that I really preferred my own company in private, she told me that extreme extroverts can flip their behaviour sometimes. I forgot what she called it but it was something like an inversion of the personality type.
I can still draw great energy when I am in a crowd and am very comfortable at public speaking because as a marketing person, I had so much experience at it, but I am more than happy with my own company and that of my wife as sole company. Gardening, woodworking and night fishing out on a boat on my own under the stars (and satellites!) are just the most wonderful experiences for me after 17 years of retirement. Even at work, the best time was Friday night when the rest of the office had gone home and I could stay late and finally be able to get some serious work done.
My sister (80+) cannot seem to be happy unless she has a constant stream of contacts with friends and other people. In this regard, I think that the old song that says, "people who need people are the luckiest people in the world" is dead wrong. They just seem to be so needy all of the time. I reckon that the better sentiment is that ""people who DON'T need people are the luckiest people in the world"