Originally Posted by david7031
That would seem to imply that you have to make a flight once every 36 months, and that mileage accrual from hotels, AmEx, etc. is not good enough.
Correct. The 'How does it work' page (also) says about Award Miles:
And they remain valid as long as you make a minimum of only one eligible flight every 3 years with KLM, Air France or any other member of the SkyTeam alliance.