I've had the same hunch. I think some memories need repeating so that you can continue remembering them. Most of the memories that I have from my early childhood are ones that I think about once in a while. I had three serious falls with a skateboard before the age of 7, but I only remember the worst of the falls. It's the one I always thought of when I was reminded of those falls (broke a tooth, so any time I look in the mirror I might be reminded of it). At this point I only remember that I did fall before the worst one and I remember the extent of my injuries, but I don't even remember the specific place of it.
I think this is exactly true. And for example if someone else is involved in the memory and you relate it to them they wonder 'how did you remember that it happened X years ago??'. But as you say it's that every now and then (at least with me) you have thought about it and reinforced the memory. The other person has not typically. Which is why they are surprised that you remember the event. So yes you 'remind' yourself I think this is true from what I experience as well.
Then, I found out about SDAM, and I was utterly devastated. I basically don't have memory when compared to other people. I can learn knowledge about something, but I can't actually remember anything, because for other people, remembering involves "re-living" that situation almost as though as if it was happening again.
SDAM stuff completely drives me crazy, as I feel that I'm missiog out on a something that is fundamental to the human life. So I just try not to think about SDAM further, and pretend that it's all a joke and everybody's experience is exactly as mine.
Ironically, this may make your "memory" of the event better than others'.
At work, people sometimes thought I had a bad memory because I wrote stuff down in a notebook...3 years later, when they couldn't remember something...well, I wrote that down, let me check. :-)
I am retired now but in my last job managing a machine learning team at Capital One, I did the same thing except using Emacs and org mode, like recording good things that my reports did for their reviews, meeting notes (usually written up after the fact), tech ideas, etc.
I also take notes on vacations, good recipes I run across, etc.
EDIT: I think the act of writing things down helps my memory, regardless of future use of notes.