Mollies live a long time, maybe forever in saltwater, I am not sure about sailfins. Those are probably bred to have sailfins and usually man made fish are not as tollerant. I could be wrong about them being man made
Sail fins (P. latipinna, P. velifera) are the natural species...although the albino, gold, and black forms are all selectively bred....you can see them in the salt marshes in Florida acting just like the killies here. I wasn't planning on using them, just curious as to whether they would be OK in a reef....