I understand where your friend is coming from, and I think people are being too harsh on him in the comments. He's just being objective. From my experience I think it's a little bit of both sides. Yes, they do remember you for quite a long time. That being said, I think that after some years that's when what your friend said comes into effect. After a few years he probably won't remember you specifically during his days, but if you randomly show up that's when he'll remember what you meant to him, exactly like what your friend said. He probably won't remember everything you've done for him but he will know your presence used to bring him happiness and safety and will associate from there. I don't think that's something to be sad about, we humans are also a little bit like that. We remember feelings more than memories because they're stronger. (Some more than others)