well don't forget that during all the star trek series they had different cast and crew on each series. where as Dark Shadows they had a set cast with special guest stars others wise it was a set cast with minor kill off's. and a big break for those who were set in the 20th cenury when they did the time travel bit which lasted a a couple season.
and they also had a book series for the series as well. and now dynamite entertainment has a comic series which is set after the series ends .