Spotify on this Windows 10 laptop can't keep my offline playlists. They still need to be downloaded every few days.
And I have one Windows 7 desktop at home, I can't see that one on my Offline devices on my account.
EDIT: And this Windows 10 laptop can't remember my last played song. It shows me the last song I've played when I FIRST played Spotify on this laptop. (New Laptop this is.)