Assuming reasonable growing conditions are met, I would think successful rebloom would be a combination of genetics, climate and length of the growing season. Climate would include all those things like rainfall, humidity, temperature. Instant rebloom should work better in areas with shorter growing seasons than rebloom with a space required by the plant between initial bloom and rebloom. A few years ago I was given an old style yellow daylily that had been grown by someone's mother for a long time. It bloomed well in late spring/early summer and then rebloomed in October. I asked the person who gave it to me and they couldn't recall that it had ever done that, but the growing season they had was shorter than mine is here. It was a nice thing and I regretted when the deer ate it to oblivion. So far, none of those that rebloomed for me on the current daylilies have waited that long to send up scapes. Sept and Oct would be nice rebloom timing in most years. I think as we get hotter and drier, any rebloom won't look as nice as initial bloom. That happened to the Galaxy Explosion rebloom last year. It succeeded, but the blooms weren't particularly attractive. By mid-July in a normal year the heat is going to be a factor.
