I don't know anybody who has kept one more than 6 months. Usually they're done after about 3 months Best left in the ocean, IMO (or at least until somebody figures out how to keep them).
I had two of them last over a year and a half. I think one died because he got stuck and couldnt get out. I have not seen the other one in a while but I wouldnt be surprised if he was just hiding some where. I did nothing special for them. They seemed to do just fine on their own.
I had a flame scallop last about a year aswell, in my first reef tank a few years back. Tank was skimmerless, I assume it survived because of the nutrient rich water, but who knows.