The statute of limitations does not toll for fugitives from justice in the federal system. If his charges were brought in federal court, your ex-husband is well advised to retain an experienced federal defense attorney who can advise him how to make the best out of a bad situation. Although I am not familiar with North Carolina law, I am sure that they handle fugitives from justice in a similar manner.
Your ex-husband should contact his former attorney to discuss the proper procedure for turning himself in. If you helped your ex-husband to flee, or you have information regarding his current location, you should consult with your own attorney before going to the authorities to avoid being charged as an accomplice. It is important that you consult with a different attorney than your ex-husband to avoid any conflict of interest.
Statue of limitations applies to the time the prosecutor has to formally charge a person with a crime. If the crime has already been charged against your ex-husband it will remain outstanding until he takes care of it.