Yes, just once in spring, at least that is what this plant has done for me. Also only on unpruned tips, too much late summer/ fall pruning will decrease flowering... I think. This one has been getting pruned only 2 times a year, once lightly before buds open and more heavily cut back mid summer when the first flush slows down.
I bought a nursery starter plant last summer with small pink blossoms that flowered all summer despite pruning to the trunk in spring so I guess there are differences between varieties. The one pictured above is mountain collected material.