This is a very good question... with no simple answer. When it comes to soft corals, as Kanga points out, they split and split and the "younger" ones grow on. So depending on how you think of an "individual's" age, how "old" the coral really is becomes a kind of philosophical question. I do believe that a single mushroom polyp can "get old"... however, I doubt too many of us keep them that long. i.e. I don't think that's the case here.