I did not say that he was a part of it for 100 years, only that he joined the FF then, at least according to Legends of Awesomeness. Oogway is said to have lived around if not more than 1000 years, so there is no reason why he would not be over 100 years old. True, if it was not for the series I would say he is more like 80 years old. Because he adopted Tai Lung more than 40 years ago when he was older than 30.
124 atleast. In one episode in Legends of Awesomeness, they celebrate him joining the Furious Five one hundred years ago.