@Monsieur_Pook It depends actually. How long you could remember something is based one how muc you repeat it and how deep or meaningful that memory is to you. There are other factors, but the most influential factor for normal people is that.
For example, i pretty much only remember the context of most of the story i read or watch. But there is exception like Mahouka, a novel that i keep rereading, and Lelouch, an anime that i could still remember the story and plot even though the last time i watch it is around 6 years ago. Those two are something means a lot to me, which made it easier for me to remember and it stuck to me until now, while other better (debatable) anime or novel doesn't really stuck to me.
Another example is how you could remember your most embarrassing or most happy memories even though you didn't even try to remember it everyday, and how you need to actually repeat your math equation just so you could remember it until exam but forget about it after that.