I've been playing the same family for the last five years. The three kids started out as triplets and I aged Hannah to child and Juliette to teen. My sim mom is my main playable character and with the release of each pack I've moved her out to focus on the new pack features. She's completed a lot of the aspirations, skills, careers, collections, etc.
https://i.imgur.com/vmGdwDH.png
After about four years I aged Juliette to young adult. She remained in the family home for a few months while I decided how to play her. With the release of the Spa Day refresh I moved her out to her own place in Winderburg. She is currently working on the new aspirations and also owns a shop selling spa related products. Juliette was my first ever second save game.
https://i.imgur.com/3eSraEi.png
Shortly after I aged Isabel to child. Not sure when I'll age them to teen.
https://i.imgur.com/0si7kPa.png
Mom has been living on a farm in Windenberg since Cottage Living released in July.
https://i.imgur.com/jrFsDuJ.png
Hannah and Isabel reside in the family home with Dad and Coco. I'm not playing them at all right now.
https://i.imgur.com/1RWjhhZ.png
I'll be moving Mom back in in the near future and then renovate their home to include space for farm animals. This is when I'll probably age up Hannah and Isabel to teen. Then young adult and move them out. They'll probably share an apartment in San Myshuno since I've never played a sim in an apartment or done the City Native aspiration.
And for anyone interested this is Juliette's teenage story.
https://forums.thesims.com/en_US/discussion/comment/17872598#Comment_17872598