I'm 52 years old, and I have diaries stretching back to 1980 (when I was all of 9 years old!). Over the years I gradually worked on transcribing them from handwriting to comupter text, and that's made them much more accessible in the present day. E.g., when my father passed away in 2020, it was so easy to just search for "Dad" and revisit long-ago snippets from the past. (And to sadly realize that I'd taken his presence for granted over the years.)

I still regret my roughly ten-year diary hiatus from 1985-1995, losing the bulk of my formative high school/college years in the process. Because as I've grown older, and those memories become more and more distant, I've lost a lot of the day-to-day detail, trivial though it may have been, of my past.