Moderator, SkyTeam and Germany
Join Date: Sep 2001
Location: FRA/STR/NUE
Programs: BA, LH, KL, EY, IHG, Marriott, Hyatt, Hilton, Radisson, H Rewards
Posts: 5,964
KLM miles do not expire. But KLM can close your account within their ToC's if you have no qualifying activity for 3 years. I'm not 100% sure what a qualifying activity is, but someone recently wrote here that it has to be a KLM or partners flight, not only 'non-flight' activity IIRC.
However I have never heard of a case where KLM had closed an acoount that hold a balance.