The Great Basin bristlecone pine of the eastern Sierra Nevada can live more than five thousand years. The giant sequoia of the western Sierra Nevada can live more than three thousand years. The familiar coastal redwood from the Coastal Ranges can live more than two thousand years. Besides impressive longevity, one thing that they all have in common is that they all eventually die.
Most trees in home gardens do not live much more than a century. Some oaks can last a long time. Willows, poplars and acacias do not. Trees typically do not live as long in landscape situations as they do naturally in the wild because their life cycles are accelerated by watering and fertilizing, and also because watering promotes rot. Some trees get removed because they grow too big.
While trees are young and growing, they sometimes need help with structural problems. They might need pruning to eliminate limbs that are likely to break away and fall. On rare occasion, trees might need pruning to reduce weight and resistance to wind if stability becomes a concern. Falling limbs or falling trees are very natural in the wild, but can be serious problems around the home.
As trees age, they develop more structural deficiencies, which are increasingly difficult to repair or accommodate. Most big old hardwood trees have some degree of decay within their main trunks, even if no such damage is visible from the outside. Although perfectly natural, this decay eventually compromises structural integrity. Stability is slowly compromised as aging roots decay.
It is true that most trees that fall or drop limbs are more likely to do so while getting thrashed by winter storms. However, there are other factors that can bring down limbs or entire trees. Warming spring weather promotes growth of new foliage, which significantly increases the weight and wind resistance of structurally deficient limbs and destabilized trees. Warmth also accelerates decay. Even after winter storms, there are many other reasons to be aware of the health of trees.