I tried ResophNotes yesterday on the more than ten thousand notes exported from ConnectedText. It worked, but not very well. It took a while for notes to open. Clicking on a link eventually opened the target note, but it took unacceptably long (even though I have a quad-core processor). Christian Tietze reports that this behavior starts with about about 1500 notes (see his comment on the previous post). I would suppose that this slow-down depends at least to some extent on the processor and memory specification of your system, but I also think that it is unacceptable for a large body of notes. More than 20,000 notes are not unheard of for a life-time of note-taking, even if you do not just copy web pages but take careful notes. Thus, Jules Verne amassed 20,000, Luhmann seems to have ended up with about 90,000. Roland Barthes with 12,0000, and Hans Blumenberg with 30,000.
In any case, it does not seem unreasonable to expect a robust note-taking or Zettelkasten-system to handle a large number of notes (with headroom to spare).