I've also retained numerous memories of significant events from early ages. But not the day-to-day events.

Were you an introspective child? Because I used to run back over my memories as I grew up, thinking through them in chronological order, just to test how much I could remember. That is probably what let them sink in and last though to my older age.

I also find it interesting that I recall my memory being better. When I was around 12, I remember being able to recall most of my childhood, but now it is just significant or emotional moments.