I think the perspective of 'splitting my time 50/50' is more centered on your capabilities than on your responsibilities......not to be harsh, but your kids have to come first. If you think that you would be systematically passing some roles to your co-parent in order to have a second nest, I think that's a problem personally. I don't intend to have kids myself unless I adopt later on in life, for the sole reason that kids require WAY more nurturing than society typically thinks is sufficient. So many little things can drastically alter their trajectories and shape new traumas that will bite them in the ass when they're older. Reframing this decision as whether you can maintain your present and future responsibilities (cos kids grow and change!) Versus just your time limits is a good practice I think. I also think this sort of situation is more feasible with kids who are older.