When they are small , not. When limbs and leaves start touching the next tree , they are beginning to crowd. If 3 sides of a tree are getting sun they generally are doing well. Where the sun don't shine, limbs die and that's nature's way of self pruning and thinning the stands of multiple trees . If you want 3 total healthy trees 50 years from now , it would take a large area. Would take a small fraction of space for the next 10 years. When they get to crowding, select the keepers and remove the less desirable manually verses waiting for nature's slower processing. Then years down the road you might need to go to 1, especially if it is a small area. The shorter time the less desirables are there you will have their shade and whatever they have to offer for that length of time and your keepers just last longer and get more magnificent with time.