Once I had an experience which freaked me out at the time... For some hours, less than a day, I heard pitches slightly differently in each ear. I have no idea what caused it, nor how it is even possible, but it scared the heck out of me. Had it continued my music career would have been over then and there. Fortunately, some hours later the problem was gone, never to reoccur.

On a more normal note, I have my good and bad hearing days, too. Some days nothing seems to sound right, or good. Most of the time, though, I think I have fairly consistent listening experiences... that is, if I think something sounds good, a listen the following day will confirm that. Of course, it's also true that if I think something sounds like crap, it probably will the following day, week, etc...