It's funny, but think there is definitely an element of truth there too. 
I've always known what I like - it's just that it keeps changing!  ;)   
Or maybe not so much changing as expanding. 
Several years ago I read a musician's comment that <i>a good song, is a good song</i> .. it caught my attention and made me look outside the box I'd made for myself, and listen to songs that I wouldn't have even tried before that.  Sometimes my old prejudices are validated, sometimes I add great new music/musicians to my "list", and sometimes I get total surprises (no way would I have expected to like Dubstep, but I do, some of it anyway).