I strongly suspect the main reason for Virgin choosing EDI as their “scottish home” was a financial carrot dangled by management to lure them away from Glasgow. As we know they don’t have any aircraft based at EDI. Profit primarily and load factors will determine how long they hang around for. They’re no different to the majority of airlines. I don’t know what the actual load factors have been for the route but I doubt they have been dreadful. Had they been way below expectation, the route would have been chopped very quickly.