I've always heard that a set consists of two dances (Mrs. Bennet "he danced the two fifth with...", etc.)and thought that a single dance is approximately 15 minutes and thus a set roughly a half hour but it was also mentioned in this GR that a single dance was 30 minutes and hence a set an hour (that's a lot of dancing!). I was just wondering which is correct? I would imagine some pieces are longer than others, naturally, but was just curious about the average.