The yaya of my nephew has been with the family since he was a newborn. Now that he is 7, there's really not much need for one. But we want to keep her around since she is now part of the family. Have you transitioned yayas into a more general role in the family even if her main skills revolve around childcare?

Yes, since we felt like our yaya was a big part of our family, we wanted to keep her with us for a long time. My mom gave her more responsibility with kitchen duties as well as budgeting. We also gave her some cleaning chores as well. But, these are minimal. She now functions more as my mom's trusted personal assistant.