Cheon Moo-Young tells Lee Rang that in 2020 he will sacrifice his life to save Lee Yeong, thus implying that Lee Yeon will continue to use him and abandon him, he also tells him that he will not live to be a century old. However, when Yeon and Rang met, Yeon was an adult and Rang was a child. (There are also see flashbacks of Yeon as a child, proving that foxes can in fact be small children that grow into adulthood) Therefore it is safe to say that Rang is over 100 years old when he dies in 2020, as he is in adult in both time lines and Yeon had been searching for his true love for 600 years and Rang's persistence that Yeon abandoned him for her. He is at least over 600 years old by the time he dies.