I have 32 multi-stem maple trees that are a nightmare to keep trimmed. They were originally planted as a hedge between this property and two others. They were already 10+ feet tall when I bought this house and each year, I struggle to keep them at that height. I even bought a Komatsu RedMAx long hadled trimmer to get to the center. It is over eight feet wide. It has been recommended that I cut it back to 7 feet, which would make it much easier to manage, but would eliminate nearly all the foliage. If I do that, will it survive and fill in at a much lower height. If so, I would make my life a lot easier. This hedge is 135 feet long. I realize that this would have to be done in the late fall when the trees are dormant.

Trees usually survive drastic pruning. Quite often even if you cut a tree clear off, the stump will sprout. I think it will work if you wait until after they have lost their leaves in the fall.

I don't think it will be a very good looking solution or last very long. Think about the common practice of topping trees. When the leaves are gone, you have ugly stubs, and then the next spring, many long branches sprout from each stub. They grow quickly, but are not solidly anchored to the stub. They frequently break off in the wind. With their well established roots, they may grow 3 feet a year quickly becoming as over grown as what you are fighting now.

If you can't let them grow, you might be better off removing them completely, and planting something else if you need the separation and privacy. Many of your flowering shrubs would look nice and would never get to where they were such a problem.