Main Branches should never be cut back to stubs. People "top" trees because they grow into power lines, over roofs, or simply because they interfere with views. Topping trees often leave behind ugly, bushy, weakly attached limbs that usually grow back higher than the original branches that were cut.
Arborists agree that topping is the worst thing you can do for the health of a tree. It starves the tree by radically reducing its food-making capability and makes the tree more vulnerable to insects and disease.
The type and regularity of tree care depends on the species, age, location, climate, and other factors that involve the tree's development. First thing to do is to learn about your trees and recognize their needs. It is vital to appreciate that proper tree care is a life long process, and that planting and caring for a tree is a long-term commitment.