https://www.metv.com/stories/in-the-early-stages-of-the-waltons-michael-learned-wanted-to-quit-the-show

The actress also revealed that she wanted to quit acting but never did.

Michael Learned eventually left the show after many years of playing Olivia. It must be difficult for an actor to day in and day out play the same exact role year after year and she played the role for 8 years. She also may I say has to go down as one of the best TV moms ever. Although I enjoyed the show after she left and when Peggy Rea came on as Rose, I think she did a stand up job filling in for the Olivia Walton character. I think what hurt the show the most was when Richard Thomas left.