The setting with the max. 9 cached tracks is the playback cache, which is only intended for short network disruptions.
There is a permanent cache where you can put stuff. If you want your playlist to be cached automatically, go to the playlist view, hit the three dots next to your playlist, and use “Configure auto offline cache”.
Symfonium has excellent offline support, I think there is no scenario left open. You can offline-cache your whole library if you want. Use the permanent cache for, well, permanent caching, and the rolling cache if you want a size-limited cache (does not work with smart playlists though). Read more about it here: Offline media cache and downloads