They are due to stress from my understanding, so I would think it is dependent on what the stress issue is. My half Marble spots ran around the perimeter when I put the divider in for the flower. It has been 5 months and they have showed much improvement but still show slightly.
a few years ago a buddy had a leo (freshly imported) develop running spots but she fully recovered..i believe it was from bad water and shipping stress.if its cheaper because of the running spots, you can save it and have a bargain!
some rays do heal up nicely but some wont.. my female Marble didn't.. it was due to the Male Marble who want to mate... one of the love bit really wound had a really bad damage..i also seen a LFS's gotten a freee motoro from it's customer and it too got a bit mark from his careless mistake of putting the ray into a Koi tank which nip it's back side but after a month it heal just like it was never damaged.