Brandon, if your doing alot of shooting I would suggest once a year! More likely it is a f.f. or modern low stretch material. They will wear out, even with good maintenance, waxing. The constant bending at the nock area seems to be a common breaking point. And being under the serving, kind of out of sight out of mind type thing!
That being said, I have had strings on bows longer than should be! Some bowyers recommend 1 year or 10,000 shots, who's counting? So I would recommend you get a new one and save that one for a back-up, already shot in and set -up, and just rotate out like that as you have the bow. Strings are cheap, broken bows aren't! Good shootin, Steve