I realized that needing every song I'd ever want to listen to on my local disk was just a form of digital hoarding. I backed up hundreds of gigabytes of my music, deleted it from my computer, and realized I never cared enough to restore it despite years of collecting and organizing it.
Bonus question: what about when this happens to a Spotify-exclusive track?
In other words with no active Spotify service even downloaded songs simply stop working.
I was even thinking of writing an open letter to Spotify to allow the user to choose 10 zombie apocalypse tracks that would Always keep working no matter what.
But, otherwise, I started to organize/curate my collection which I've largely not done anything to speak of with for literally years. (And which is messed up in various ways.) And I sort of came to the conclusion that it didn't really matter that much at this point.