Here's a related story:
An old school friend and I got together to watch the total eclipse.
We were talking about our memories, and I explained that I use my older sister and mother as benchmarks.
That is, I have a feeling for how my sister's memory is (ten years older—74) and how my mother's memory was before she died (age 92. She'd read a book and you could give her the same book, and she'd happily read it again, not remembering that she already read it).
IOW, I felt that as long as I was above that glide path, I wouldn't worry.
Then I stopped, and asked my friend, "Did I tell you that before?"
He said, "Yeah. Twice!"