Why do some of you want to kill off the best cast members. That's just dumb. We watch shows, partly because of the script but mostly because we like/identify with the actors playing the roles.
There was a Britcom on BBC a few years ago called Coupling. Season one was pretty good but one of the main stars quit after one year. They replaced him and season 2 was ok but a definite downgrade. Fast forward a few years and they brought the show to America with an American cast. The pilot was almost word for word as the British version but none of the actors was likable. Show failed. Not even sure it finished one season.
Bottom line, the ACTORS make the show. So, stop trying to kill off the main characters!