Trimming or pruning, both terms are correct, is important to the health of your tree as well as it's ornamental and aesthetic value. The removal of dead or damaged limbs from your tree helps insure they do not fall on your home or worse yet your family. Damaged limbs that break off and leave a stub can never properly compartmentalize and heal, and present an entry way for disease and decay.
Trimming your tree for good structural health when it is young can prevent a great deal of hardships down the road. The establishment of good scaffolding branches and a strong central leader, should be done in that first ten (10) years after planting. Don't worry though, it is almost never too late to properly trim your tree. Corrective pruning can solve a lot of problems, even if your trees have been neglected for sometime.
Have a certified arborist evaluate your trees for health and structural soundness today.