Moisture stress in those locations is high, due to wind and low precipitation. The trees are adapted to these environmental stresses. They produce tough, long-lasting needles. Their dense, resinous wood makes them especially resistant to attack by insects and fungi. They are able to withstand damage from lightening strikes and wind.
Many bristlecone pines live to be about 1000 years old, but there are individuals that are more than 4000 years old. The oldest living bristlecone pine is 4,765 years old. The high resin content and density of the wood, combined with the dryness of the environment, prevent even the dead trees from rotting. Some of these remain standing for years.