> Probably not long. I might also make it clear I'm not a fan, but at the end of the day, they're generally within their rights to record me in public. Sucks, but not much I can do.

You should not test this. If you record someone for hours or days in public, you may find yourself with a restraining order, a ticket for stalking (or assault), or a civil suit for invasion of privacy or IIED or something similar. This depends on the jurisdiction and the person you are recording, but what you are citing about not having an expectation of privacy is mostly meant with regards to point-in-time instances (one photo), not ongoing continuous surveillance.

Yes, the only distinction between any and all of these things and a legal recording is the length of time and the invasiveness of the collection of data. No, there is no bright line where you are definitely guilty or definitely safe (few things in law have one).