If both parents truly support shared parenting the effort towards making that happen would be equal. Bashing the other parent or fearing the kids might like it there too much is not an equal effort. Doing what is best for the child is an equal effort.
Worrying is carrying tomorrow's load with today's strength — carrying two days at once. It is moving into tomorrow ahead of time. Worrying does not empty tomorrow of its sorrow; it empties today of its strength. ("The Hiding Place")