It's kind of sad to see yourself growing bored of a long-time fixation, but like you said, it's bound to happen sooner or later, no point in trying to go against it.
Still, touhou has a way of sticking with you, fanart of the characters online, or the music and its many covers. For me at least these things inevitably, given enough time, build up the nostalgia needed to pull me back into the games for a while.
Though I'll probably never play them with the same vigor as when first discovering them.