Why was Saffy still playing the long suffering daughter shtick in her 20s and 30s in the later seasons?

The problem with Saffy is that while she did have a point in the early seasons, her refusal to leave the house and live on her own does mean Julia Salwahla might have been correct in her assessment of Saffy, that she enjoyed the comfort of living off her mother.

Look up the Season 3 finale, she couldn't adapt to living at the college campus. After you reach adulthood, you can't keep on blaming your mother for everything that goes wrong in your life.