Bonus miles: Valid for 30 years
If you collected bonus miles from the Dutch airline KLM in the past, you had to be busy. Why? After a period of 20 months without "extending activities", the miles would just be cancelled.
The Austrian Verein für Konsumenteninformation (VKI) took legal action against this practice. The supreme court (OGH) now decided in favour of the VKI on all questions. It stated that the jurisdiction for vouchers applies to bonus miles as well. This means that they have to be valid for 30 years and the airline is not allowed to reduce this time frame.
The decision is legally binding. You can read the full text of the verdict here (in German language).
If you collected bonus miles from KLM and they were unlawfully cancelled, you can protest by referring to the verdict of the HG Vienna from 13.10.2015 (case 39 Cg 43/14p).