I'm sorry to have doubted you. Good luck dealing with Lufthansa. They are the "flagship" of the Star Alliance and as such should step up if they're at fault in any way.
In the interim I did some checking on the expiration policy of Miles & More program. It's vague to say the least. It's not clear if the expiry is renewable or rolling. With most US carriers as long as one has some activity before the expiry date the "clock is re-set" and all miles remain valid until the new expiry date. If I'm reading Lufthansa's T&C's correctly their miles seem to expire regardless of activity. It's a use them or lose them situation.
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