There are some espaliered apple trees still producing fruit after 150 years. When looked after properly, espaliered trees can have an incredibly long lifespan. The strong branches are less likely to break, which accounts for the tree's longevity.  Having the branches so spread out also helps the airflow in the tree and, therefore, means fewer insect and disease problems. A spaced-out branch structure also makes finding and dealing with diseased branches faster and more manageable.