10,000 YEAR OLD ENDOLITHS. “Some endoliths have extremely long lives. In August 2013 researchers reported evidence of endoliths in the ocean floor with a generation time of 10,000 years. These are slowly metabolizing, not in a dormant state.” (Endoliths are extremophiles living inside rock).
http://en.m.wikipedia.org/wiki/List_of_longest-living_organisms