At that point I just didn't find it worth it even visiting. Finding more didn't seem like something I wanted to do.
I also do get a trickle of new accounts. I recognize a name after appreciating their threads a few times, and then click through to their profile and read a bit to increase my sample size. If it turns out I got a skewed sample, I unfollow them using the same process I described above.
This process really feels like almost no work, and I've gotten enormous benefits from it. Most concretely, it's been trivial to frontrun traditional media and public health recommendations by several months during the entirety of the pandemic. I can pretty much credit my Twitter feed with myself and my extended family getting through the pandemic much more safely and healthily (incl mental health) than we likely would otherwise have.
The main cost is that this isn't conducive to a very large following list, but perhaps that's a good thing.