I'm sure that could be part of it, but also something that I learned recently, taking ibuprofin (among other over the counter drugs) for extended periods of time can also cause it. I take ibuprofin (both OTC and Rx) on a daily basis for back problems. Not much I can do about it.
For me, the ringing is pretty much constant. The only time I ~don't~ hear it is when I'm listening to music or watching a movie. Otherwise, I'm always reminded of it. Sometimes it's worse than other times, but rarely do I ~not~ hear something.