On rating things out of 5 stars

So I have this kind of OCD thing that I have to rate all my tracks in iTunes. (I don't want to stream. I don't want to depend on the network to play music). I clearly know what's a 3, but sometimes I can't figure out if a great track is really a 5, or a great 4. I've finally come on a heuristic to separate them: If I wished there was a 6th star, then it's really a 5. If not, then it's just a 4.