Agreements made between divorcing spouses are generally looked upon favorably by the divorce courts. However, when it comes to child support, most states take the position that parents cannot agree to waive the child support payment obligations. This is based on the principle that both parents have a duty to support their children.
Child support payments are meant to provide for the financial needs of your child and are calculated according state formulas. Some divorcing parents mistakenly believe that if they don't accept child support, the noncustodial parent won't have visitation rights, but visitation is a legal right, so it sn't dependent on support payments. Because the focus is on the child and not the wishes of the parents, generally, you have no ability to waive child support during a divorce. The same rationale applies to support orders currently in place -- the court is not likely to cancel an existing child support obligation because you request that payments stop.
Child support ordinarily lasts until the child graduates from high school or reaches the age of majority. While a child support order is in place, the recipient parent is generally obliged to accept payments. If that parent chooses to refuse payments, the other parent may bring this behavior to the court's attention. In these cases, a judge has the authority to either provide penalties for noncompliance or even modify the custody order, if modifying it is consistent with the best interests of the child.