On a side note, if you are at an intersection in NC, if you are not behind the big white line (which can be different for the left turn lane,) and well behind where you think it should be, you won't trip the sensor. People tend to creep up when the light doesn't change quickly, and they move off the sensor and it never trips. Furthermore, I would wait a lot more than 3 cycles before I ran it (like 10-15 minutes.)
As to the actual record question, convictions stay on forever, different items require a look-back of different periods. For instance 3 years is the look back period for insurance and work driving records. When you get a traffic record for court, it goes back 7 years. DWI's go back forever. Insurance looks back 3 years for PJC's to determine if you can use a new one.
Not a lawyer, this isn't legal advice, been to traffic court a lot.