Older trees tend to recover from cuts and wounds more slowly than younger trees. When a tree is young and vibrant it generally produces living tissue more rapidly and is capable of compartmentalizing a wound faster than an older tree. As the tree ages the regeneration of living plant tissue slows, leaving cuts and wounds exposed for longer periods of time. The longer a tree has a wound that is open the more susceptible it is to being infected by pathogens and harmful insects.
On older trees we recommend cleaning the crown – the removal of all the dead, damaged, diseased wood, and, branches that cross, rub against other branches or otherwise appear to be growing in an direction that is or would later harm the tree.
Unless it is a completely unruly tree, storm damaged or there is a specific problem, we avoid making large cuts into living plant tissue on older trees except whens it absolutely necessary.