Thanks to Floyd and Charlie for reposting their very insightful thoughts here.
Being an analytical kind of guy, I love hearing someone else's analysis of why a song does or doesn't work.
Floyd, one of the jaw-dropping observations you made was about songs that are more than 6 months to a year old. That was a wakeup call to me, because I tend to think in longer spans than that. But, now that you've said it, it makes sense... and it also makes me realize how unaware I am of the past 6 months trends in music.