It’s probably more related to how the hardware stores the software; the strength of a memory depends on the strength (complexity) in the interconnectivity of neurons related to that memory. The more some piece of information relates to other information, the physically stronger the connection of neurons that make up that information become.

Prior to 3ish our brains are focused on the foundations needed to form memories; sensory perception, language, etc. Once we start converting collections of senses and language into experiences it probably reaches a threshold where those pathways are complex enough to last, and continually reinforced or built upon, for a lifetime.