I started my rotational save at launch and re-started in 2016, 2018 and 2022. But I always have between one and three side saves that aren't meant to last, that's why I consider myself a serial restarter regardless.
The side saves use always the same pool of sims: The Windenburg premades, a small collection of Maxis gallery sims and since 2018 also my Detroit sims. I'm very attaced to this bunch and enjoy playing them in different parallel universes. Tossing the same old sims into vastly different circumstances brings out aspects of their personalities that they'd probably never shown me otherwise.
My reason for starting over my rotational saves was in each case too much change. I don't like playing generationally, aging is off and time progresses very slowly. But even so, at some point the first generation is gone, and the story has progressed from struggling to pay the bills to most, if not all, of my sims being in positions where they can dictate global politics. Then it's time to reset.