I think of it as a time-decay function. There are only so many attentive, focused hours one can give during a day, and a memory only lasts so long before it de

I think of it as a time-decay function. There are only so many attentive, focused hours one can give during a day, and a memory only lasts so long before it decays from disuse. Some amount of area under this curve represents what a person can functionally retain. It isn't a fixed amount, as more connections between subjects tends to reinforce both, but there is a limit.