I'm not diagnosed as an Aspie - just considering whether I should be evaluated. I do have some long-term threads of interest that may or may not be "special interest" status.
I'll give you just one example - not necessarily one that consumes my time the most, though.
Rainbows.
Since childhood, it has always pleased me to see all the colors lined up. I would take pictures of rainbows when they occurred, and over time I learned the names of rainbow-like weather phenomena as sundogs and Brocken spectres and halos around the sun or moon. In childhood I collected crystal prisms that refracted light into rainbows. I also had various interesting lamps - including some that either projected a rainbow on the wall or could be adjusted to show any color. I have a Pinterest board of nothing but different color wheels. Once I found myself lining up bits of debris on the beach by color. I have a string of rainbow crystal beads hanging from my rearview mirror. As a kid my favorite stone was the opal and the bismuth sold in rock stores - both having a rainbow-like appearance. I collected mussel shells with iridescent, rainbow-y interiors. I learned about the iridescence of hummingbird feathers. I had glasses that made everything look rainbow-y. I would stare at CDs and the rainbow light they projected when in the sun. I recently learned that during sunset, a rainbow can be totally red. As child I adored holograms (which are rainbow-y), and the hologram-product store in the mall was one of my favorite places to go. To this day I recall several scenes in movies, shows or videogames that involved a rainbow. My favorite level in the videogame Mario 64 was the one with all the rainbows and flying. In MarioKart, it was Rainbow Road.
I don't wear rainbow stuff because I'm not homosexual and I don't want to send an inaccurate message. But I would do so, if not for that concern about misrepresenting myself (I'm asexual).
None of that rainbow-ness, however, led to me being an expert in anything. It was always just a source of joy and a piece of my identity. In contrast, music and drawing have been with me a long time too, and each led to some level of ability (e.g., my avatar on this site is my drawing of myself - though I left my hair white instead of coloring it to show that it's really brown).