Although your Butterfly Bush is an actual shrub, I've found (here in the western U.S.) that it's better treated as a perennial such as a Type 3 Clematis. You'll need to mulch the plant in the winter (ours are heavily mulched but we see tempertures of -20 to -30 degrees F) and when you're certain the plant is dormant, cut it back to the ground. chances are it will die back to the ground anyway. Buddlia blooms best on new wood. Be cautious of suckers, since, if they start they can choke off the main plant. Not only that the bush reproduces by seed and can become very invasive if not managed aggressively.
There are numerous varietals of the bush and all have differing bloom characteristics and since it's a hybrid, the bloom exposition may change slghtly from year to year.
You may wish to look at other colors of this bush, especially the Nanho Purple, which is fairly new and reamains smaller than the average 5 to 6 foot Buddlia.
You might also check to see if your nursery has a Dwarf Burning Bush... very nice little flowers and the leaves turn brilliant red in the fall. Winterberry Holly is a strinkingly beautiful bush, but you'll need at least two of them since both the male and female are required for the desired red berry production... there are several others.
Best of luck!