Answer: I'm a daylily fan so I don't know if I'd agree that there might be something better, but there sure are lots of long blooming perennials for you to chose from:
coreopsis verticillata Zagreb
penstemon varieties (Apple Blossom, Sour Grapes, Midnight, hardy when in a dry position in winter)
geranium Russel Pritchard
Asters x Frikartii M?nch and Wunder von St?fa
Echinacea purpurea "Magnus"
Salvia micropylla varieties
Scabiosa "butterfly Blue"
gypsophila Bristol Fairy
Gaura "whirling Butterflies"
Verbena Bonariensis (reseeds, not 100 % hardy)
Ligularia "The Rocket"
Kierengoshoma (Yellow Waxbells)
I'm sure there are others, but these are most reliable.
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