But I want to argue that the fact that characters come and go is actually a strength The Waltons has and is something which really adds to the show. There are so many great moments in The Waltons that wouldn't exist if the cast had remained intact throughout the whole thing: John-Boy's quiet 'goodnight' to the family from the episode when he leaves (The Achievement), John's loneliness after Olivia's absence and then his extreme happiness when he enjoys a brief phone call with her (The Legacy), Ester's return to the show after having been gone for over a year due to illness (Grandma Comes Home) or the moment when the whole family says a little goodbye to Zebulon after he'd died, which was due to the real life death of actor Will Geer (The Empty Nest). The absence of some of the characters even means that their mere appearance is something to look forward to in future episodes, meaning that you're really made to appreciate every one of them.
The fact that things change so often is, for me, one of the show's main appeals. In real life you can't stay with the same people forever and the time will come when you have to say goodbye to them. The Waltons, for me, is one of the few shows which accurately represents this aspect of life, eventually a time will come, in all relationships when you have to say goodbye to the other person, or when there'll be a significant change to your everyday life; both things happen several times in The Waltons and this is just one of the reasons I count it as one of my favourite TV shows.