Research suggests that people who live to be 80 years old have passed through 71 percent of the subjective experience of the passage of time by the time they're 40; the years between ages 60 and 80 feel like just 13 percent of life.
This is oddly specific, isn't it? It's true that I remember a lot more about the years when I was 19 to around 30 than the decades since. Some of that is because I moved a lot & had locations to anchor myself. Now I'm doing well to remember if something happened this century. And of course, there's more new stuff happening in the earlier years & novelty stands out in that subjective flow. Pretty much all adult firsts happened to me after I was 18.
This feels like half an essay. I'll try to come back to it with more coherent thoughts.