Autistic Hedgehog

Well, I can only speak for myself, but not only do my interests tend to shift, they come in different levels. Like, I get very surface fixations, and then I’ll want stuff to do with that fixation, and that can be as simple as buying a bunch of things in a color I’m fixated on. Other things run much deeper, and I’ll continue learning about them and being interested in them my whole life. 

Like, for example, there was a period where I was fixated on owls, and wanted to collect lots of owl stuff. That waned. But I’ve been interested in history and archaeology for a long time, and though sometimes I don’t spend a lot of time on it, it always comes back. (I also have a very special place in my heart for maritime disasters.)

Very few of my interests go away, but the intensity of them changes. I’ve heard of other autistics who, for example, learn everything they can about a special interest and then aren’t interested anymore. Based on what I know about my followers, my guess is that there are a lot of different (and perfectly normal) ways that we interact with our special interests. So I’d guess that your experience is no more unusual than any of ours.