This can be a VERY important task when it comes to Mature old Growth Trees with Lots of Lateral growth and heavy limbs. Supporting the canopy with a state of the art cable system can be a good preventavive to help your Young or Mature Trees to maintain good structure .  Cable system will help with exccesive swaying in high winds. Also a safety factor for reassuince that Large limbs or tops will not separate during high winds. Bracing comes into factor when the tree is Splitting appart hence a cable system and sometimes on large splits where tree can be saved a proper install of threaded rod with nuts to pull split back together. Not all trees have to be cut down if shown signs of splits and high flex in winds. Have Your Trees Accesed Annually . We highly preach to homeowners to just keep a eye on there trees. Trees are a very important piece of your property providing Shade , Oxygen, cover, habitat, and a nice appearance to property.