If you have final orders, they apply until the children are 18 and you are expected to actively follow them, not just passively. That means you're required to positively encourage the children to spend time with the other parent, and this obligation is outlined in the paperwork attached to your orders.
If you were to go back to court, you would need to satisfy the requirements of Rice & Asplund, which holds that there must have been a significant change in circumstances so that current orders no longer meet the best interests of the child in order for the court to consider changing final orders.
There is no age whereby a child's opinion is solely followed by the court. It will only ever give consideration to their opinion among many other factors. On average, the age where the court grants more significant weight is 12, provided the child is deemed old enough and mature enough to make informed decisions.
These views are acquired from the child by a psychologist and then passed on to the court in a family report.
Hope this helps.