I believe Princess Astrid has personally confirmed that certain items she and her sister have from their mother and grandmother are essentially on lifetime loan and will revert to the main line on her death, as indeed it is assumed some of her sister's jewels have.

http://trondni.blogspot.com/2014/09/royal-jewels-princess-astrids-aigrettes.html

In 1968 there was a formal division of the jewels of Queen Maud and Princess Martha between the current King and his two sisters - I wonder why at that time a decision was not made to establish a trust or foundation to hold the jewels, thereby not necessitating agreements for lifetime loans and allowing the two sisters of the King to have use of the jewels. Such formal arrangements existed in Sweden and the UK.

Has what happened in 1968 established a precedent as to what will happen when Queen Sonja dies, will the jewels be divided between her son and daughter and certain items given to Princess Martha Louise for her lifetime?