The oldest humans are reported to be around 120 years old, so around there I guess. Some scientists think genes may determine how old a person can live to, so it might not just be about being healthy and not having disease.
The oldest person in the world now is an American woman named Besse Cooper at 115 years old. Genes and environment seem to play a role in determining how long someone lives. So having family members with long lifespans and leading a healthy lifestyle may lead to a long life. Also, females tend to live longer than males!