In any case where a court suspends the imposition or execution of a sentence, it may fix the period of suspension for up to the statutory maximum period for which the defendant might originally have been sentenced to be imprisoned; however, the court may fix the period of suspension for a period not to exceed three years for a violation of § 18.2-67.4 or 18.2-67.4:2. The limitation on the period of suspension shall not apply to the extent that an additional period of suspension is necessary for the defendant to participate in a court-ordered program.