Whether you've made a mistake or not depends on your point of view, really. Parthenocissus is a rampant plant, and I've lost count of the number of properties in gardens I've been caring for which have had a big problem in their attic or loft, or at least under the roof, because it has been allowed to grow unattended. It has a tendency to get into the roof space, either under the fascia board or over the guttering, through small spaces, and then it can continue to grow up there, eventually causing leaks. If you want a house covered in this, then regular maintenance (involving ladders, twice a year clipping and restraining/training) is, I'd say, essential.

I agree, depends on if it is doing any damage under the roof. Pruning is essential to keep it in control.

We have Boston Ivy on the back wall of the house. We have it cut back every year when it gets to gutter level. Apart from anything else, it would completely obscure the windows. When Boston Ivy reaches the top of what it's climbing, it suddenly turns into a large-leafed plant - quite different from when it is less mature. I really like it, though.