You asked two questions. First, there is no statute of limitations on felonies in NC. Your second question is not as easy to answer. Everyone has a right to a speedy trial; in reality, though, no one seems to get one anymore. You should find a lawyer in your county to review your case.
The statute of limitations applies to the amount of time a person can be charged with a crime, not how long the state has to prosecute a person who has already been charged. It can be continued as many times as the judge will allow.
I will only address your second question as the other lawyers have answered regarding the lack of any statute of limitations on conspiracy to commit common law robbery. Common Law Robbery is a Felony and the Superior Court has jurisdiction over felonies. The District Attorney's Office controls the the calendar and the Assistant District Attorneys have free reign to call cases for plea and trial in the order that they choose. This is very frustrating for defense attorneys and our clients who are subject to the State's control when it comes to calendaring.