In the US, patents don't just "run out", the patent owner has to actively not bother tweaking something trivial, filing for a new patent on top of their own whi

In the US, patents don't just "run out", the patent owner has to actively not bother tweaking something trivial, filing for a new patent on top of their own while it's still active, and then start arguing that even though the old patent runs out, folks who act on that are now in violation of the new patent.