The soap genre has changed drastically since DS. While it's possible to get a retake or two if needed, they shoot episodes way out of sequence, so it's sometimes difficult for the actors to keep track of where they are in the story. Forget about changing your hairstyle or even getting a suntan because you need to match the way you looked in footage that was already shot. Some actors can handle that, some can't.
Kristen has expressed an interest on going back to General Hospital to finish up Starr's story. No idea when or if that might happen, as the show has an overabundance of characters as it. TPTB also seem to feel that it might be too confusing for the audience for Kristen to reappear as Starr, while her OLTL father Roger Howarth is playing a different character.
