I've been with my high school bf for years. We're both in our mid-thirties now with kids and a house. No complaints.
We did separate for a year a while back because I was paranoid that we'd "settled too fast" and never really got to experience different relationships. I didn't want to hit our 40s and have that thought creep up, so the split happened. We were in our mid twenties, and just ended up missing each other and hanging out anyway. I dated one or two guys for a brief time and meh.
In the end, I think the short time apart was good for solidifying things? Or something? We have a great relationship, I think. We do talk about everything, and we don't hold passive aggressive little grudges. We share chores, share responsibilities with the kids, and have our own individual hobbies. We respect each other's alone time, and really enjoy what we do together.
I think high school loves can last. It might not happen for everyone, but it certainly isn't unheard of.