Pruning before buds set will delay flowering and shorten height therefore less staking needed. i.e. cut coneflowers back in early June and they will bloom into September. Cut back in early July and they will bloom into October.
In late spring or early summer: certain branching perennials respond well to pinching, forcing more branching and lateral growth and shorter size when blooming. — From RS Garden Club 2017-18 Yearbook