I like rebloom, but it's not a requirement for me. If they are strong growers and easy bloomers and have a relatively long period of bloom it would be enough for me. They can manage a long period of bloom by staggering the scapes coming up in a clump, by having lots of buds that successfully reach bloom or by having those scapes just blooming at slower intervals among the buds it has. I need them to make clumps, so the growth is a factor.
The plants really do go about doing it differently. I considered Lillian's Vapor Trail the best this year, but it didn't have the longest bloom period. There were three initial bloom scapes and three instant rebloom scapes that started blooming before the first ones finished. There should have been four scapes of each, but hail and insects got two scapes. That might have affected the length of bloom which began May 22 and ended June 26. Just over a month, but quite the show in between those dates. The next two were about equal in my rating, but did it differently. Serge Rigaud bloomed from May 27 through July 20. There were five scapes and another that hail took out. There were days when there was lots of bloom, days when there were only one or two and some days the scapes took a day or two of rest. The bloom period wasn't solid bloom. I frankly enjoyed those breaks because there were other plants blooming. The other really good show came from Primal Scream which only had five scapes that bloomed from May 31 through June 26. That was the shortest bloom period of the three, but it came as a daily blast without any breaks and was just spectacular while doing it. I think given another year or two, all of these will do better and yield longer bloom periods provided natural disasters don't interfere too much.
What would be nice for me is some later rebloom as opposed to instant rebloom. I think both the blooms and myself would appreciate the cooler temperatures from later rebloom. With the long growing season here, that should work. So far, all the rebloom stalks have shown up before the initial stalks have finished blooming, but I grew an old yellow one a few years ago and it had a distinct early bloom and later fall bloom with a couple of months separating them. Wish the deer hadn't found it.