I always set my alarm each night, and I haven't heard it go off in about 6 years. I always wake up before my alarm would go off, without fail. Even if I set it

I always set my alarm each night, and I haven't heard it go off in about 6 years. I always wake up before my alarm would go off, without fail. Even if I set it to a strange time. I think it has to do with the fact that I set it each night, but I'm not sure...