Hmmm... I don't really feel like I've "peaked"; but have experienced lots of ebbing and flowing as different things take priority in life at different times. When I was a new mom, I didn't have time, energy, or money to devote to my own looks and closet. Same was true when I was a starving college student. I felt more experimental in high school because I was trying to identify my identity, as most teens do. Agree that it feels ageist and sexist to generalize.
I did hear an interesting take on how style develops for each person in a recent interview with Caroline De Maigret. She said, (and I am paraphrasing), as you go through life, you come across things you identify with, whether they are characters in movies or books, music you gravitate towards, or beautiful architecture or places around you - some things just 'speak' to you. As you seek out ways to style yourself, those things you've identified with in your life are there, and can show through you, whether you seek it out on purpose or not.