Rewatcher, first Reddit rewatch.
So I had a nice long post written out but I couldn't get the damn spoiler format right and I lost the post so screw it. I din't need those 90 minutes of my life anyhow. I've watched this show more times than I care to admit. It's probably my favorite anime. The Bandai DVDs were the first anime series that I ever physically owned, and though I've since moved on to Funimation's collector's edition Blu-ray, those DVDs are still really special to me. I've also read the light novels. They're great reads if you're interested in continuing the story after Disappearance.
As for this episode itself, it's just a great introduction to (most) of our cast of characters. Kyon's snarky straight man and Haruhi's mild sociopathy eccentricity play great off of each other and they make a great pair. Even so, the best is yet to come. There's also a ton of little details for rewatchers and light novel readers to pick up on. Seemingly insignificant lines turn into really clever foreshadowing that you'd never pick up on on the first go through. Overall just a great first episode to a great anime.
And so we're clear, Haruhi is best girl and Asakura is best class rep. Second best girl doesn't appear in the anime so I can't really talk about her. That is all.
Oh yeah, question. I just kind of grew out of it. I think I was 11? Maybe 12. Might've been older than Kyon's little sister.