As described in many other discussions here the pure core of the features necessary for long term usage of DC at local device:
- limit number of messages per chat (X) (user setting)
- introduce user function to mark messages with star(s) (still existing in database)
- delete oldest messages when number of messages gets > X when new message arrives for dedicated chat (but never delete starred ones).
- manual possibility to start housekeeping function (This is now (v1.8.1 android) only possible by exporting backup).