Thanks for the feedback, unfortunately we can only handle 1 feature request per topic, otherwise it's impossible to manage the received kudos / give the idea a proper status.
If you want to start a general feedback topic, that's great! But please use the respective help forum then. ;)
Also make sure to use the search function, since a lot of ideas might already be out there in the ideas forum. In your case, check out for example this idea: http://community.spotify.com/t5/Spotify-Ideas/Smart-Offline-Mode-for-Mobile-Apps/idi-p/25675 ;)