Different strokes for different folks, and so on, and so on and shooby dooby dooby. Oooooh sha sha.
Sorry, some may not be old enuf to remember that song.
But what I was trying to say is that I'm sure lots of diifernt corals have different lifespans. Some grow as earlier established polyps may die off. But it still looks like the coral is enlarging. Some just spread.
Really hard to say anything about lifespans. It depends on water, circulation, light, who's picking on it, whether fragged or not. Bunch of different variables that could make a dif, but hard to say how long a given coral will live.
"Life may not be the party we hoped for but while we are here we might as well dance!"