A song that you never get tired of. I am kind of over-thinking this one, because there are a few songs I have definitely liked for 20 years or so. Once I've been listening to a song for ages, rather than getting tired of it, I'm more likely to feel warm towards it because it's so much part of my life. At the same time, there are a few songs I've got into more recently, which I expect to always love, but I can't be sure that I won't ever get tired of them.
So I think the best candidates are:
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