Because they presented such a danger to society, most Vampires were destroyed long before the outer limits of their life span were determined. Ancient history offers some clues, however. In Ancient China, there was said to be one Vampire in the emperor's court through the entire (eastern) Zhou Dynasty, which would put his age at 550. More accurate modern records have certified Vampires of over 200 years old.
Vampiric longevity is the result of an ability to ward off both the DNA damage that occurs during cell division in normal humans and the damage caused by ionization. The protective caps on the ends of chromosomes known as telomeres get chewed up over time in humans, but not in vampires. HVV plasmids switch on the gene which controls the production of telomerase (an enzyme that prevents chromosome degeneration) and boosts its effectiveness with a version of its own in the packet of genetic material that fuses with the host's chromosomes. This completely prevents cellular senescence and therefore gives every cell replicative immortality. Genetic alterations also result in a biochemistry that completely protects the cells from free radicals and ambient radiation, preventing any oxidative and ionization damage to the DNA of a Vampire. In addition, in Vampires the functions of the genetic sequences responsible for the metabolic processes of aging are completely inhibited. So as a Vampire lives, cell division can continue indefinitely allowing cell damage to be repaired effectively leading to the cessation of somatic aging during the Vampiric coma.