My in-laws had planted these trees in the late 60's or early 70's believing that what they were planting was a hedge. Well, they grew and grew and became mammoth trees. It wasn't until 8 years ago when we discovered that this actually was a hedge - all that was missing was the "trimming"!!!!
This is proof - Trimming is Important.
When they are not trimmed - The hedge below grows into these giant trees seen above. (Seriously - I wouldn't have believed it either if I hadn't witnessed it myself).