From experience I can tell it vanishes. My friend gave me his old account when he quit, went from Sub to Preferred and his characters lost their rested XP.
Yes but does it truly vanish? Or is it saved for you once you resubb?
i stopped playing for over a year, came back and resubbed then logged back on and all my chars had rested exp to full it seemed like. So did it save it for me because i could have played before that but of course i would be pref and not a sub