If you and your spouse divorce when your child is very young, the parenting plan you agree on will almost certainly need to be modified as they get older. Precisely when those changes need to be made will depend on your child's needs, and to some degree, their wishes.
One family law attorney says that parents typically need to alter their parenting plan as their children transition into their preteen/early teen years. That's when most kids develop an identity and interests separate from their parents. Their extracurricular activities and friends are probably taking up more of their time.
The parenting plan you worked out when your child was in their toddler/preschool years may have focused on consistency and predictability, which are important to young children. You may have worked out a schedule that involved frequent exchanges so that your child didn't have to be apart from either parent for more than a few days. That plan might continue to work (perhaps with a little more flexibility) through their grade school years.
If you haven't made any modifications to your child's parenting plan by the time they are ready to enter high school, it may be a good idea to review the current plan and see what changes need to be made to reflect your child's schedule.
It's typically a good idea to let your child weigh in on any modifications you're considering. However, ultimately, the modifications should be determined by you and your co-parent.
As kids get farther into their teen years, you may need to make more modifications. This is a tumultuous time, and a child may need one parent more than the other. Once they're able to drive, they may be able to move between their parents' homes on their own. However, it's still important for everyone to agree on what the custody arrangement and parenting plan are.
Parenting plans need to adapt to reflect children's changing maturity levels, interests and needs. Both parents may feel their child pulling away and work harder to spend as much time with them as possible. However, it's essential to focus on what's best for your child rather than compete with your co-parent for more custody time.
If you believe that it's time to make some modifications in your parenting plan as your child enters the new school year, talk with your co-parent and work with your family law attorney.