Hmm....very good question....In the past I had a "big problem" - when I was listening to full albums there were songs from it that I simply didn't like ......however, I was keeping them in my computer...I was thinking "I'll give those songs another chance" but I realised that this is a wrong perception..
Even if you like only one song from an artist, keep it..you don't have to keep the entire discography...
I still have to clean some space on my computer.....