There is no statute or case law addressing this specific issue. However, that said, your boyfriend was entitled/is entitled to a probable cause hearing. If he has had a probable cause hearing, then there are still a number of ways that his case needs to be addressed, but that depends on a number of factors that you have not provided information on:
1. if his case is still pending in district court, then his attorney needs to object to any continuances by the state. However, this does not prevent them from indicting your boyfriend and continuing with his case in Superior Court, nor does that prevent him from being re-arrested and held upon the same indictment, and in could in fact compromise his jail credit.
2. Have the probable cause hearing - however, this has the possibility of putting your boyfriend in legal limbo - meaning District Court no longer has jurisdiction and Superior Court's jurisdiction is unclear since it is still not indicted.
3. A bond hearing - again, it is unclear how many bond hearings your boyfriend has had, but the lack of movement on the case is something the judge can consider. Again, this is dependent on the District Court having jurisdiction.
4. A speedy trial motion - there is literally no case law on this issue for a felony in District Court. I know, I have researched it extensively. However, it may be worth filing it and bringing it to the court's attention and begin the process of showing how long the case has been pending. It may also get some traction depending on the judge.
A number of these can be done together, or separately. If for whatever reason your boyfriend does not have a lawyer, that has to be addressed. You need to address these questions with his attorney. Good luck.